/* ==========================================================================
   RemoSync -- Base Design System v1.0
   ==========================================================================
   Load order:
     1. fonts.css        -- @font-face declarations
     2. base.css         -- THIS FILE (reset, tokens, layout, components)
     3. theme-*.css      -- Theme-specific custom property overrides
   ==========================================================================
   Naming convention:  --rs-{category}-{variant}
   Categories: bg, surface, text, accent, border, shadow, overlay, glow,
               radius, space, font, z, transition, anim
   ========================================================================== */

/* ==========================================================================
   1. CSS RESET (Modern Minimal)
   ========================================================================== */

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  line-height: 1.15;
  -webkit-text-size-adjust: 100%;
  -moz-tab-size: 4;
  tab-size: 4;
  scroll-behavior: smooth;
}

body {
  min-height: 100vh;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img,
picture,
video,
canvas,
svg {
  display: block;
  max-width: 100%;
}

input,
button,
textarea,
select {
  font: inherit;
  color: inherit;
}

.rs-password-toggle {
  color: var(--rs-text-secondary);
  transition: color var(--rs-transition-fast), background-color var(--rs-transition-fast), border-color var(--rs-transition-fast);
}

.rs-password-toggle:hover,
.rs-password-toggle:focus-visible {
  color: var(--rs-text-primary);
}

.rs-password-toggle[data-rs-revealed="true"] {
  color: var(--rs-accent-primary);
}

.rs-password-toggle__icon {
  width: 1rem;
  height: 1rem;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.85;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.rs-password-toggle__slash {
  opacity: 0;
  transition: opacity var(--rs-transition-fast);
}

.rs-password-toggle[data-rs-revealed="true"] .rs-password-toggle__slash {
  opacity: 1;
}

button {
  cursor: pointer;
  border: none;
  background: none;
}

a {
  color: inherit;
  text-decoration: none;
}

ul,
ol {
  list-style: none;
}

h1, h2, h3, h4, h5, h6 {
  overflow-wrap: break-word;
  font-size: inherit;
  font-weight: inherit;
}

p {
  overflow-wrap: break-word;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

/* Remove default fieldset/legend styling */
fieldset {
  border: none;
  padding: 0;
  margin: 0;
}

/* ==========================================================================
   2. CSS CUSTOM PROPERTIES -- ROOT TOKENS
   Default values follow the Minimalist Dark palette.
   Theme files override these via :root[data-rs-theme][data-rs-mode] selectors.
   ========================================================================== */

:root {
  /* --- Spacing Scale (4px base) --- */
  --rs-space-1:  4px;
  --rs-space-2:  8px;
  --rs-space-3:  12px;
  --rs-space-4:  16px;
  --rs-space-5:  20px;
  --rs-space-6:  24px;
  --rs-space-8:  32px;
  --rs-space-10: 40px;
  --rs-space-12: 48px;
  --rs-space-16: 64px;

  /* --- Border Radius --- */
  --rs-radius-none: 0;
  --rs-radius-sm:   4px;
  --rs-radius-md:   8px;
  --rs-radius-lg:   12px;
  --rs-radius-xl:   16px;
  --rs-radius-2xl:  24px;
  --rs-radius-full: 9999px;

  /* --- Z-Index Layers --- */
  --rs-z-three:        -1;
  --rs-z-base:          0;
  --rs-z-content:      10;
  --rs-z-sticky:       20;
  --rs-z-dropdown:     30;
  --rs-z-overlay:      40;
  --rs-z-overlay-tools: 50;
  --rs-z-modal:        60;
  --rs-z-toast:        70;
  --rs-z-tooltip:      80;
  --rs-z-spotlight:    85;
  --rs-z-pointer:      90;

  /* --- Transitions --- */
  --rs-transition-fast:   150ms ease;
  --rs-transition-normal: 250ms ease-in-out;
  --rs-transition-slow:   400ms ease-in-out;
  --rs-transition-theme:  0ms;

  /* --- Typography Scale (Major Third 1.25) --- */
  --rs-font-size-xs:   0.75rem;    /* 12px */
  --rs-font-size-sm:   0.875rem;   /* 14px */
  --rs-font-size-base: 1rem;       /* 16px */
  --rs-font-size-md:   1.125rem;   /* 18px */
  --rs-font-size-lg:   1.25rem;    /* 20px */
  --rs-font-size-xl:   1.5rem;     /* 24px */
  --rs-font-size-2xl:  1.875rem;   /* 30px */
  --rs-font-size-3xl:  2.25rem;    /* 36px */
  --rs-font-size-4xl:  3rem;       /* 48px */

  /* --- Line Heights --- */
  --rs-leading-tight:   1.25;
  --rs-leading-snug:    1.375;
  --rs-leading-normal:  1.5;
  --rs-leading-relaxed: 1.625;
  --rs-leading-loose:   1.75;

  /* --- Letter Spacing --- */
  --rs-tracking-tight:   -0.025em;
  --rs-tracking-normal:   0;
  --rs-tracking-wide:     0.025em;
  --rs-tracking-wider:    0.05em;
  --rs-tracking-widest:   0.1em;

  /* --- Font Weights --- */
  --rs-font-regular:  400;
  --rs-font-medium:   500;
  --rs-font-semibold: 600;
  --rs-font-bold:     700;

  /* --- Font Families (overridden per theme) --- */
  --rs-font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  --rs-font-family-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', 'Courier New', monospace;
  --rs-font-family-display: var(--rs-font-family);

  /* --- Default Colors (Minimalist Dark) --- */
  /* Backgrounds */
  --rs-bg-primary:   #111111;
  --rs-bg-secondary: #1a1a1a;
  --rs-bg-tertiary:  #0d0d0d;

  /* Surfaces */
  --rs-surface-1: #1e1e1e;
  --rs-surface-2: #252525;
  --rs-surface-3: #2c2c2c;

  /* Text */
  --rs-text-primary:   #f0f0f0;
  --rs-text-secondary: #a0a0a0;
  --rs-text-muted:     #666666;
  --rs-text-inverse:   #111111;

  /* Accent */
  --rs-accent-primary: #3b82f6;
  --rs-accent-hover:   #60a5fa;
  --rs-accent-active:  #2563eb;
  --rs-accent-muted:   rgba(59, 130, 246, 0.15);

  /* Accent Secondary */
  --rs-accent-secondary:       #3b82f6;
  --rs-accent-secondary-hover: #60a5fa;

  /* Borders */
  --rs-border-default: #2e2e2e;
  --rs-border-subtle:  #1f1f1f;
  --rs-border-strong:  #444444;
  --rs-border-accent:  #3b82f6;

  /* Shadows */
  --rs-shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --rs-shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --rs-shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.5);

  /* Overlay */
  --rs-overlay-bg: rgba(17, 17, 17, 0.85);

  /* Semantic States */
  --rs-success: #22c55e;
  --rs-warning: #f59e0b;
  --rs-error:   #ef4444;
  --rs-info:    #3b82f6;
}

/* ==========================================================================
   3. BASE TYPOGRAPHY
   ========================================================================== */

body {
  font-family: var(--rs-font-family);
  font-size: var(--rs-font-size-base);
  font-weight: var(--rs-font-regular);
  line-height: var(--rs-leading-normal);
  letter-spacing: var(--rs-tracking-normal);
  color: var(--rs-text-primary);
  background-color: var(--rs-bg-primary);
}

h1 {
  font-size: var(--rs-font-size-4xl);
  font-weight: var(--rs-font-bold);
  line-height: var(--rs-leading-tight);
  letter-spacing: var(--rs-tracking-tight);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-6);
}

h2 {
  font-size: var(--rs-font-size-3xl);
  font-weight: var(--rs-font-semibold);
  line-height: var(--rs-leading-tight);
  letter-spacing: var(--rs-tracking-tight);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-5);
}

h3 {
  font-size: var(--rs-font-size-2xl);
  font-weight: var(--rs-font-semibold);
  line-height: var(--rs-leading-snug);
  letter-spacing: var(--rs-tracking-normal);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-4);
}

h4 {
  font-size: var(--rs-font-size-xl);
  font-weight: var(--rs-font-medium);
  line-height: var(--rs-leading-snug);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-4);
}

h5 {
  font-size: var(--rs-font-size-lg);
  font-weight: var(--rs-font-medium);
  line-height: var(--rs-leading-normal);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-3);
}

h6 {
  font-size: var(--rs-font-size-md);
  font-weight: var(--rs-font-medium);
  line-height: var(--rs-leading-normal);
  text-transform: uppercase;
  letter-spacing: var(--rs-tracking-wider);
  color: var(--rs-text-secondary);
  margin-bottom: var(--rs-space-3);
}

p {
  font-size: var(--rs-font-size-base);
  line-height: var(--rs-leading-normal);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-4);
}

a {
  color: var(--rs-accent-primary);
  text-decoration: none;
  transition: color var(--rs-transition-fast);
}

a:hover {
  color: var(--rs-accent-hover);
  text-decoration: underline;
}

small {
  font-size: var(--rs-font-size-sm);
  color: var(--rs-text-muted);
}

code,
kbd,
samp,
pre {
  font-family: var(--rs-font-family-mono);
  font-size: 0.9em;
}

code {
  padding: 2px 6px;
  border-radius: var(--rs-radius-sm);
  background: var(--rs-surface-2);
  color: var(--rs-accent-primary);
}

pre {
  padding: var(--rs-space-4);
  border-radius: var(--rs-radius-md);
  background: var(--rs-surface-1);
  border: 1px solid var(--rs-border-default);
  overflow-x: auto;
  margin-bottom: var(--rs-space-4);
}

pre code {
  padding: 0;
  background: none;
  color: inherit;
}

strong, b {
  font-weight: var(--rs-font-semibold);
}

em, i {
  font-style: italic;
}

hr {
  border: none;
  border-top: 1px solid var(--rs-border-default);
  margin: var(--rs-space-8) 0;
}

/* Teacher content -- prioritizes readability */
.rs-content {
  font-size: var(--rs-font-size-md);
  line-height: var(--rs-leading-relaxed);
  max-width: 72ch;
}

/* ==========================================================================
   4. LAYOUT UTILITIES
   ========================================================================== */

.rs-container {
  width: 100%;
  max-width: 1280px;
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--rs-space-6);
  padding-right: var(--rs-space-6);
}

.rs-container--narrow {
  max-width: 720px;
}

.rs-container--wide {
  max-width: 1440px;
}

/* --- Grid --- */
.rs-grid {
  display: grid;
  gap: var(--rs-space-4);
}

.rs-grid--2 {
  grid-template-columns: repeat(2, 1fr);
}

.rs-grid--3 {
  grid-template-columns: repeat(3, 1fr);
}

.rs-grid--4 {
  grid-template-columns: repeat(4, 1fr);
}

.rs-grid--auto-fill {
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
}

/* --- Flex --- */
.rs-flex {
  display: flex;
}

.rs-flex--center {
  align-items: center;
  justify-content: center;
}

.rs-flex--between {
  align-items: center;
  justify-content: space-between;
}

.rs-flex--col {
  flex-direction: column;
}

.rs-flex--wrap {
  flex-wrap: wrap;
}

.rs-flex--gap-2 {
  gap: var(--rs-space-2);
}

.rs-flex--gap-4 {
  gap: var(--rs-space-4);
}

.rs-flex--gap-6 {
  gap: var(--rs-space-6);
}

/* --- Sidebar Layout --- */
.rs-sidebar-layout {
  display: flex;
  min-height: 100vh;
  isolation: isolate;
}

.rs-sidebar-layout__sidebar {
  width: 240px;
  flex-shrink: 0;
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  z-index: var(--rs-z-sticky);
  background: var(--rs-bg-secondary);
  border-right: 1px solid var(--rs-border-default);
  padding: var(--rs-space-6) 0;
  overflow-y: auto;
  transition: width var(--rs-transition-normal);
}

.rs-sidebar-layout__main {
  flex: 1;
  margin-left: 240px;
  padding: var(--rs-space-6);
  min-width: 0;
}

.rs-sidebar-layout__sidebar ul {
  display: flex;
  flex-direction: column;
  gap: var(--rs-space-1);
  padding: 0 var(--rs-space-3);
  margin: 0;
}

.rs-sidebar-layout__sidebar hr {
  border: 0;
  border-top: 1px solid var(--rs-border-subtle);
  margin: var(--rs-space-4) var(--rs-space-4);
}

.rs-sidebar-utility {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 999px;
  border: 1px solid transparent;
  color: var(--rs-text-secondary);
  text-decoration: none;
  transition: background var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              color var(--rs-transition-fast),
              transform 80ms ease-in,
              box-shadow var(--rs-transition-fast);
}

.rs-sidebar-utility svg {
  width: 17px;
  height: 17px;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.8;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.rs-sidebar-utility:hover {
  background: var(--rs-surface-1);
  border-color: var(--rs-border-default);
  color: var(--rs-text-primary);
}

.rs-sidebar-utility:active {
  transform: translateY(1px);
}

.rs-sidebar-utility--active {
  color: var(--rs-accent-primary);
  background: var(--rs-accent-muted);
  border-color: color-mix(in srgb, var(--rs-accent-primary) 30%, transparent);
  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--rs-accent-primary) 20%, transparent);
}

.rs-sidebar-footer {
  display: flex;
  flex-direction: row;
  align-items: center;
  gap: 10px;
  padding: 0 var(--rs-space-3);
}

.rs-sidebar-utility--danger:hover {
  color: var(--rs-error);
  border-color: color-mix(in srgb, var(--rs-error) 28%, transparent);
  background: color-mix(in srgb, var(--rs-error) 10%, transparent);
}

.rs-sidebar-utility--danger svg {
  width: 16px;
  height: 16px;
  stroke-width: 2;
}

.rs-sidebar-link {
  display: flex;
  align-items: center;
  min-height: 44px;
  padding: 0 var(--rs-space-4);
  border: 1px solid transparent;
  border-radius: var(--rs-radius-md);
  color: var(--rs-text-secondary);
  text-decoration: none;
  font-size: var(--rs-font-size-sm);
  font-weight: var(--rs-font-medium);
  transition: background var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              color var(--rs-transition-fast),
              transform 80ms ease-in,
              box-shadow var(--rs-transition-fast);
}

.rs-sidebar-link:hover {
  background: var(--rs-surface-1);
  border-color: var(--rs-border-default);
  color: var(--rs-text-primary);
}

.rs-sidebar-link:active {
  transform: translateX(1px);
}

.rs-sidebar-link--active {
  background: linear-gradient(90deg, var(--rs-accent-muted), transparent);
  border-color: color-mix(in srgb, var(--rs-accent-primary) 30%, transparent);
  color: var(--rs-text-primary);
  box-shadow: inset 3px 0 0 var(--rs-accent-primary);
}

.rs-sidebar-link--accent {
  color: var(--rs-accent-primary);
}

.rs-sidebar-link--accent:hover {
  background: var(--rs-accent-muted);
  border-color: color-mix(in srgb, var(--rs-accent-primary) 35%, transparent);
}

.rs-dashboard-tools {
  display: inline-flex;
  align-items: center;
  gap: var(--rs-space-2);
}

.rs-dashboard-tool {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 999px;
  border: 1px solid var(--rs-border-default);
  background: var(--rs-surface-1);
  color: var(--rs-text-secondary);
  text-decoration: none;
  transition: background var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              color var(--rs-transition-fast),
              transform 80ms ease-in,
              box-shadow var(--rs-transition-fast);
}

.rs-dashboard-tool:hover {
  color: var(--rs-text-primary);
  border-color: color-mix(in srgb, var(--rs-accent-primary) 28%, transparent);
  background: var(--rs-accent-muted);
  box-shadow: var(--rs-shadow-sm);
}

.rs-dashboard-tool:active {
  transform: translateY(1px);
}

.rs-dashboard-tool--subtle {
  background: transparent;
}

.rs-dashboard-tool__icon {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.8;
  stroke-linecap: round;
  stroke-linejoin: round;
}

/* ==========================================================================
   5. FORM BASE STYLES
   ========================================================================== */

label {
  display: block;
  font-size: var(--rs-font-size-sm);
  font-weight: var(--rs-font-medium);
  color: var(--rs-text-primary);
  margin-bottom: var(--rs-space-2);
}

input[type="text"],
input[type="email"],
input[type="password"],
input[type="search"],
input[type="url"],
input[type="number"],
input[type="tel"],
select,
textarea {
  display: block;
  width: 100%;
  height: 44px;
  padding: 0 var(--rs-space-4);
  font-size: var(--rs-font-size-base);
  line-height: 44px;
  color: var(--rs-text-primary);
  background: var(--rs-surface-1);
  border: 1px solid var(--rs-border-default);
  border-radius: var(--rs-radius-md);
  transition: border-color var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast);
  outline: none;
}

textarea {
  height: auto;
  min-height: 100px;
  padding: var(--rs-space-3) var(--rs-space-4);
  line-height: var(--rs-leading-normal);
  resize: vertical;
}

select {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23a0a0a0' stroke-width='2'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  background-size: 16px;
  padding-right: 40px;
}

input:focus,
select:focus,
textarea:focus {
  border-color: var(--rs-accent-primary);
  box-shadow: 0 0 0 3px var(--rs-accent-muted);
}

input::placeholder,
textarea::placeholder {
  color: var(--rs-text-muted);
}

/* Validation states */
input.rs-input--error,
select.rs-input--error,
textarea.rs-input--error {
  border-color: var(--rs-error);
  box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.15);
}

input.rs-input--success,
select.rs-input--success,
textarea.rs-input--success {
  border-color: var(--rs-success);
}

/* Help text below inputs */
.rs-input-help {
  font-size: var(--rs-font-size-sm);
  color: var(--rs-text-muted);
  margin-top: var(--rs-space-1);
}

.rs-input-help--error {
  color: var(--rs-error);
}

/* --- Buttons --- */
.rs-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--rs-space-2);
  height: 44px;
  padding: 0 var(--rs-space-6);
  font-size: var(--rs-font-size-base);
  font-weight: var(--rs-font-medium);
  line-height: 1;
  border-radius: var(--rs-radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background-color var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              color var(--rs-transition-fast),
              transform 80ms ease-in,
              box-shadow var(--rs-transition-fast);
  white-space: nowrap;
  user-select: none;
}

.rs-btn:active {
  transform: scale(0.97);
}

.rs-btn:disabled,
.rs-btn--disabled {
  opacity: 0.5;
  pointer-events: none;
  cursor: not-allowed;
}

/* Primary button */
.rs-btn--primary {
  background: var(--rs-accent-primary);
  color: var(--rs-text-inverse);
  border-color: var(--rs-accent-primary);
}

.rs-btn--primary:hover {
  background: var(--rs-accent-hover);
  border-color: var(--rs-accent-hover);
}

.rs-btn--primary:active {
  background: var(--rs-accent-active);
}

/* Secondary button */
.rs-btn--secondary {
  background: transparent;
  color: var(--rs-text-primary);
  border-color: var(--rs-border-default);
}

.rs-btn--secondary:hover {
  background: var(--rs-surface-2);
  border-color: var(--rs-border-strong);
}

/* Danger button */
.rs-btn--danger {
  background: var(--rs-error);
  color: #ffffff;
  border-color: var(--rs-error);
}

.rs-btn--danger:hover {
  filter: brightness(1.1);
}

/* Danger outline button */
.rs-btn--danger-outline {
  background: transparent;
  color: var(--rs-error);
  border-color: var(--rs-error);
}

.rs-btn--danger-outline:hover {
  background: rgba(239, 68, 68, 0.1);
}

/* Ghost button */
.rs-btn--ghost {
  background: transparent;
  color: var(--rs-text-secondary);
  border-color: transparent;
}

.rs-btn--ghost:hover {
  background: var(--rs-surface-1);
  color: var(--rs-text-primary);
}

/* Button sizes */
.rs-btn--sm {
  height: 36px;
  padding: 0 var(--rs-space-4);
  font-size: var(--rs-font-size-sm);
}

.rs-btn--lg {
  height: 52px;
  padding: 0 var(--rs-space-8);
  font-size: var(--rs-font-size-lg);
}

.rs-btn--full {
  width: 100%;
}

/* ==========================================================================
   6. COMPONENT BASE STYLES
   ========================================================================== */

/* --- Card --- */
.rs-card {
  background: var(--rs-surface-1);
  border: 1px solid var(--rs-border-default);
  border-radius: var(--rs-radius-lg);
  padding: var(--rs-space-6);
  box-shadow: var(--rs-shadow-sm);
  transition: box-shadow var(--rs-transition-fast),
              border-color var(--rs-transition-fast);
}

.rs-card:hover {
  box-shadow: var(--rs-shadow-md);
}

.rs-card--flat {
  box-shadow: none;
}

.rs-card--flat:hover {
  box-shadow: none;
}

.rs-card__header {
  margin-bottom: var(--rs-space-4);
  padding-bottom: var(--rs-space-4);
  border-bottom: 1px solid var(--rs-border-subtle);
}

.rs-card__title {
  font-size: var(--rs-font-size-lg);
  font-weight: var(--rs-font-semibold);
}

.rs-card__body {
  color: var(--rs-text-secondary);
}

.rs-card__footer {
  margin-top: var(--rs-space-4);
  padding-top: var(--rs-space-4);
  border-top: 1px solid var(--rs-border-subtle);
}

.rs-course-detail-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--rs-space-3);
  align-items: center;
  justify-content: flex-end;
}

.rs-course-create-form {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--rs-space-5);
  align-items: start;
  width: 100%;
  max-width: none;
}

.rs-course-create-form__stack {
  display: grid;
  gap: calc(var(--rs-space-4) + 2px);
  min-width: 0;
}

.rs-course-create-form__row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) max-content;
  gap: var(--rs-space-4);
  align-items: stretch;
}

.rs-course-create-form__field {
  display: grid;
  gap: var(--rs-space-3);
  min-width: 0;
}

.rs-course-create-form__actions {
  display: flex;
  align-items: stretch;
  justify-content: flex-start;
}

.rs-course-create-form__actions .rs-btn {
  min-width: 152px;
  height: 48px;
}

.rs-switch-card {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  column-gap: calc(var(--rs-space-5) + 2px);
  min-height: 72px;
  padding: var(--rs-space-4) var(--rs-space-5);
  border-radius: var(--rs-radius-lg);
  border: 1px solid var(--rs-border-default);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.035), transparent 100%),
    color-mix(in srgb, var(--rs-surface-1) 86%, var(--rs-bg-secondary) 14%);
  box-shadow: var(--rs-shadow-sm);
  cursor: pointer;
  transition: border-color var(--rs-transition-fast),
              background-color var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast),
              transform 120ms ease;
}

.rs-switch-card:hover {
  border-color: var(--rs-border-strong);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.045), transparent 100%),
    color-mix(in srgb, var(--rs-surface-2) 90%, var(--rs-bg-secondary) 10%);
  box-shadow: var(--rs-shadow-md);
}

.rs-switch-card:focus-within {
  border-color: var(--rs-accent-primary);
  box-shadow: 0 0 0 3px var(--rs-accent-muted), var(--rs-shadow-md);
}

.rs-switch-card__content {
  display: flex;
  flex-direction: column;
  gap: 5px;
  min-width: 0;
  max-width: 36ch;
}

.rs-switch-card__title {
  font-size: var(--rs-font-size-sm);
  font-weight: var(--rs-font-semibold);
  color: var(--rs-text-primary);
  letter-spacing: var(--rs-tracking-wide);
  text-transform: uppercase;
}

.rs-switch-card__hint {
  display: block;
  font-size: var(--rs-font-size-xs);
  line-height: 1.45;
  color: var(--rs-text-secondary);
}

.rs-switch-card__control {
  position: relative;
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.rs-switch-card__input {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  cursor: pointer;
}

.rs-switch-card__track {
  position: relative;
  display: inline-flex;
  align-items: center;
  width: 54px;
  height: 32px;
  padding: 3px;
  border-radius: var(--rs-radius-full);
  border: 1px solid var(--rs-border-default);
  background: var(--rs-surface-2);
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.18);
  transition: background-color var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast);
}

.rs-switch-card__thumb {
  width: 24px;
  height: 24px;
  border-radius: var(--rs-radius-full);
  background: var(--rs-text-muted);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.18);
  transition: transform var(--rs-transition-fast),
              background-color var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast);
}

.rs-switch-card__input:checked + .rs-switch-card__track {
  border-color: color-mix(in srgb, var(--rs-accent-primary) 45%, var(--rs-border-default));
  background: color-mix(in srgb, var(--rs-accent-primary) 14%, var(--rs-surface-2));
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.08), 0 0 0 1px color-mix(in srgb, var(--rs-accent-primary) 10%, transparent);
}

.rs-switch-card__input:checked + .rs-switch-card__track .rs-switch-card__thumb {
  transform: translateX(22px);
  background: var(--rs-accent-primary);
  box-shadow: 0 8px 18px rgba(0, 0, 0, 0.18);
}

.rs-switch-card__input:focus-visible + .rs-switch-card__track {
  box-shadow: 0 0 0 3px var(--rs-accent-muted);
}

.rs-switch-card--course {
  align-self: stretch;
  justify-self: start;
  width: max-content;
  min-width: 0;
}

.rs-switch-card--compact {
  min-height: 44px;
  padding: 0 var(--rs-space-4) 0 var(--rs-space-5);
  border-radius: var(--rs-radius-md);
  column-gap: var(--rs-space-4);
}

.rs-switch-card--compact .rs-switch-card__content {
  max-width: none;
  gap: 0;
}

.rs-switch-card--course .rs-switch-card__title {
  white-space: nowrap;
}

.rs-course-list-card__footer {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--rs-space-4);
  align-items: end;
}

.rs-course-list-card__stats {
  margin-bottom: 0;
}

.rs-course-list-card__actions {
  display: flex;
  justify-content: flex-end;
  align-self: end;
}

.rs-course-list-card__actions .rs-btn {
  min-width: 0;
  padding-inline: var(--rs-space-3);
}

.rs-assignment-list {
  display: grid;
  gap: var(--rs-space-3);
}

.rs-course-lessons-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--rs-space-5);
}

.rs-course-lessons-pane {
  min-width: 0;
}

.rs-course-lessons-pane__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--rs-space-3);
  margin-bottom: var(--rs-space-4);
}

.rs-course-lessons-pane__header h5 {
  margin: 0;
  font-size: var(--rs-font-size-sm);
  font-weight: var(--rs-font-semibold);
  letter-spacing: var(--rs-tracking-wide);
  text-transform: uppercase;
  color: var(--rs-text-secondary);
}

.rs-assignment-disclosure {
  border: 1px solid var(--rs-border-default);
  border-radius: var(--rs-radius-lg);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.02), transparent 100%),
    color-mix(in srgb, var(--rs-surface-1) 90%, var(--rs-bg-secondary) 10%);
  box-shadow: var(--rs-shadow-sm);
  overflow: hidden;
}

.rs-assignment-disclosure__summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--rs-space-3);
  padding: var(--rs-space-4);
  cursor: pointer;
  list-style: none;
}

.rs-assignment-disclosure__summary::-webkit-details-marker {
  display: none;
}

.rs-assignment-disclosure__label {
  font-size: var(--rs-font-size-sm);
  font-weight: var(--rs-font-semibold);
  color: var(--rs-text-primary);
}

.rs-assignment-disclosure__body {
  padding: 0 var(--rs-space-4) var(--rs-space-4);
}

.rs-assigned-lessons-list {
  display: grid;
  gap: var(--rs-space-3);
}

.rs-assigned-lesson {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--rs-space-3);
  align-items: center;
  min-height: 72px;
  padding: var(--rs-space-4);
  border-radius: var(--rs-radius-lg);
  border: 1px solid color-mix(in srgb, var(--rs-accent-primary) 22%, var(--rs-border-default));
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.04), transparent 100%),
    color-mix(in srgb, var(--rs-accent-primary) 8%, var(--rs-surface-1));
  box-shadow: var(--rs-shadow-sm);
}

.rs-assigned-lesson__meta {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 5px;
}

.rs-assigned-lesson__title {
  margin: 0;
  font-size: var(--rs-font-size-sm);
  font-weight: var(--rs-font-semibold);
  color: var(--rs-text-primary);
}

.rs-assigned-lesson__details {
  display: flex;
  flex-wrap: wrap;
  gap: var(--rs-space-2) var(--rs-space-3);
  align-items: center;
  font-size: var(--rs-font-size-xs);
  color: var(--rs-text-secondary);
}

.rs-assigned-lesson__actions {
  display: flex;
  align-items: center;
}

.rs-assignment-option {
  position: relative;
  display: grid;
  grid-template-columns: 24px minmax(0, 1fr);
  align-items: center;
  gap: var(--rs-space-4);
  min-height: 64px;
  padding: var(--rs-space-4) var(--rs-space-4);
  border-radius: var(--rs-radius-lg);
  border: 1px solid var(--rs-border-default);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.03), transparent 100%),
    color-mix(in srgb, var(--rs-surface-1) 88%, var(--rs-bg-secondary) 12%);
  box-shadow: var(--rs-shadow-sm);
  cursor: pointer;
  transition: border-color var(--rs-transition-fast),
              background-color var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast),
              transform 120ms ease;
}

.rs-assignment-option:hover {
  border-color: var(--rs-border-strong);
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.045), transparent 100%),
    color-mix(in srgb, var(--rs-surface-2) 90%, var(--rs-bg-secondary) 10%);
  box-shadow: var(--rs-shadow-md);
}

.rs-assignment-option:has(.rs-assignment-option__input:focus-visible) {
  border-color: var(--rs-accent-primary);
  box-shadow: 0 0 0 3px var(--rs-accent-muted), var(--rs-shadow-md);
}

.rs-assignment-option:has(.rs-assignment-option__input:checked) {
  border-color: color-mix(in srgb, var(--rs-accent-primary) 48%, var(--rs-border-default));
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.05), transparent 100%),
    color-mix(in srgb, var(--rs-accent-primary) 10%, var(--rs-surface-1));
  box-shadow: 0 10px 26px color-mix(in srgb, var(--rs-accent-primary) 12%, transparent);
}

.rs-assignment-option__input {
  position: absolute;
  inset: 0;
  opacity: 0;
  cursor: pointer;
}

.rs-assignment-option__check {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  border-radius: 8px;
  border: 1px solid var(--rs-border-default);
  background: color-mix(in srgb, var(--rs-surface-2) 90%, var(--rs-bg-secondary) 10%);
  color: transparent;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, 0.14);
  transition: border-color var(--rs-transition-fast),
              background-color var(--rs-transition-fast),
              color var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast),
              transform 120ms ease;
}

.rs-assignment-option__check svg {
  width: 14px;
  height: 14px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.rs-assignment-option__input:checked + .rs-assignment-option__check {
  border-color: color-mix(in srgb, var(--rs-accent-primary) 52%, var(--rs-border-default));
  background: color-mix(in srgb, var(--rs-accent-primary) 16%, var(--rs-surface-2));
  color: var(--rs-accent-primary);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--rs-accent-primary) 10%, transparent);
}

.rs-assignment-option__meta {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 5px;
}

.rs-assignment-option__title {
  font-weight: var(--rs-font-semibold);
  color: var(--rs-text-primary);
}

.rs-assignment-option__details {
  display: flex;
  flex-wrap: wrap;
  gap: var(--rs-space-2) var(--rs-space-3);
  align-items: center;
  font-size: var(--rs-font-size-xs);
  color: var(--rs-text-secondary);
}

.rs-course-assignment-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--rs-space-3);
  align-items: center;
}

.rs-theme-thumb {
  position: relative;
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.06), transparent 72%),
    var(--rs-surface-2);
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.rs-theme-thumb__glow,
.rs-theme-thumb__panel,
.rs-theme-thumb__line {
  position: absolute;
  display: block;
  pointer-events: none;
}

.rs-theme-thumb__glow {
  inset: 0;
  opacity: 0.9;
}

.rs-theme-thumb__panel {
  top: 16px;
  left: 16px;
  right: 16px;
  bottom: 24px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.08);
}

.rs-theme-thumb__line {
  left: 24px;
  height: 6px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.18);
}

.rs-theme-thumb__line--short {
  width: 32%;
  bottom: 24px;
}

.rs-theme-thumb__line--long {
  width: 48%;
  bottom: 12px;
}

.rs-theme-selector {
  max-width: 1180px;
}

.rs-theme-card {
  min-height: 184px;
  display: flex;
  flex-direction: column;
  gap: var(--rs-space-2);
}

.rs-theme-card__meta {
  gap: var(--rs-space-2);
}

.rs-theme-card__modes {
  margin-top: auto;
}

[data-rs-theme-preview="minimalist"] {
  background:
    linear-gradient(180deg, rgba(59, 130, 246, 0.18), transparent 45%),
    linear-gradient(180deg, #161616, #101010);
}

[data-rs-theme-preview="minimalist"] .rs-theme-thumb__panel {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.06);
}

[data-rs-theme-preview="minimalist"] .rs-theme-thumb__line {
  background: rgba(255, 255, 255, 0.22);
}

[data-rs-theme-preview="hacker"] {
  background:
    repeating-linear-gradient(
      180deg,
      rgba(0, 255, 65, 0.06),
      rgba(0, 255, 65, 0.06) 2px,
      rgba(0, 0, 0, 0) 2px,
      rgba(0, 0, 0, 0) 4px
    ),
    linear-gradient(180deg, #0d130d, #080b08);
}

[data-rs-theme-preview="hacker"] .rs-theme-thumb__panel {
  background: rgba(0, 255, 65, 0.04);
  border: 1px solid rgba(0, 255, 65, 0.18);
  box-shadow: 0 0 18px rgba(0, 255, 65, 0.12);
}

[data-rs-theme-preview="hacker"] .rs-theme-thumb__line {
  background: rgba(0, 255, 65, 0.42);
}

[data-rs-theme-preview="3d"] {
  background:
    radial-gradient(circle at 18% 20%, rgba(0, 255, 65, 0.24), transparent 32%),
    radial-gradient(circle at 80% 26%, rgba(118, 255, 170, 0.18), transparent 30%),
    linear-gradient(135deg, rgba(2, 10, 7, 0.96), rgba(7, 24, 17, 0.82));
}

[data-rs-theme-preview="3d"] .rs-theme-thumb__panel {
  background: linear-gradient(135deg, rgba(5, 18, 13, 0.72), rgba(10, 30, 22, 0.52));
  border: 1px solid rgba(0, 255, 65, 0.22);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  box-shadow: 0 0 18px rgba(0, 255, 65, 0.08), 0 0 26px rgba(118, 255, 170, 0.05);
}

[data-rs-theme-preview="3d"] .rs-theme-thumb__line {
  background: linear-gradient(90deg, rgba(0, 255, 65, 0.46), rgba(118, 255, 170, 0.28));
}

[data-rs-theme-preview="academic"] {
  background:
    linear-gradient(180deg, rgba(192, 149, 64, 0.2), transparent 42%),
    linear-gradient(180deg, #2a2419, #1a1710);
}

[data-rs-theme-preview="academic"] .rs-theme-thumb__panel {
  background: rgba(255, 248, 232, 0.06);
  border: 1px solid rgba(192, 149, 64, 0.18);
}

[data-rs-theme-preview="academic"] .rs-theme-thumb__line {
  background: rgba(232, 224, 208, 0.3);
}

[data-rs-theme-preview="synthwave"] {
  background:
    linear-gradient(180deg, rgba(255, 56, 160, 0.28), transparent 35%),
    linear-gradient(0deg, rgba(91, 33, 182, 0.3), transparent 40%),
    linear-gradient(180deg, #241739, #120a22);
}

[data-rs-theme-preview="synthwave"] .rs-theme-thumb__glow {
  background:
    linear-gradient(180deg, transparent 58%, rgba(56, 189, 248, 0.2) 58%, rgba(56, 189, 248, 0.2) 60%, transparent 60%),
    linear-gradient(90deg, rgba(56, 189, 248, 0.12), transparent 32%, transparent 68%, rgba(255, 56, 160, 0.16));
}

[data-rs-theme-preview="synthwave"] .rs-theme-thumb__panel {
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 56, 160, 0.24);
  box-shadow: 0 0 20px rgba(56, 189, 248, 0.12);
}

[data-rs-theme-preview="synthwave"] .rs-theme-thumb__line {
  background: rgba(255, 255, 255, 0.28);
}

/* --- Modal --- */
.rs-modal-backdrop {
  position: fixed;
  inset: 0;
  z-index: var(--rs-z-modal);
  background: rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--rs-space-4);
  animation: rs-fade-in 200ms ease-out;
}

.rs-modal {
  background: var(--rs-bg-secondary);
  border: 1px solid var(--rs-border-default);
  border-radius: var(--rs-radius-lg);
  box-shadow: var(--rs-shadow-lg);
  width: 100%;
  max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  padding: var(--rs-space-8);
  animation: rs-scale-in 200ms ease-out;
}

.rs-modal__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--rs-space-6);
}

.rs-modal__title {
  font-size: var(--rs-font-size-xl);
  font-weight: var(--rs-font-semibold);
}

.rs-modal__close {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--rs-radius-md);
  color: var(--rs-text-muted);
  transition: color var(--rs-transition-fast),
              background var(--rs-transition-fast);
}

.rs-modal__close:hover {
  color: var(--rs-text-primary);
  background: var(--rs-surface-2);
}

.rs-modal__body {
  margin-bottom: var(--rs-space-6);
}

.rs-modal__footer {
  display: flex;
  gap: var(--rs-space-3);
  justify-content: flex-end;
}

/* --- Toast / Notification --- */
.rs-toast-container {
  position: fixed;
  top: var(--rs-space-4);
  right: var(--rs-space-4);
  z-index: var(--rs-z-toast);
  display: flex;
  flex-direction: column;
  gap: var(--rs-space-2);
  pointer-events: none;
}

.rs-toast {
  pointer-events: auto;
  padding: var(--rs-space-3) var(--rs-space-4);
  border-radius: var(--rs-radius-md);
  background: var(--rs-surface-2);
  border: 1px solid var(--rs-border-default);
  box-shadow: var(--rs-shadow-md);
  font-size: var(--rs-font-size-sm);
  color: var(--rs-text-primary);
  max-width: 400px;
  display: flex;
  align-items: center;
  gap: var(--rs-space-3);
  animation: rs-slide-in-right 250ms ease-out;
}

.rs-toast--success {
  border-left: 3px solid var(--rs-success);
}

.rs-toast--error {
  border-left: 3px solid var(--rs-error);
}

.rs-toast--warning {
  border-left: 3px solid var(--rs-warning);
}

.rs-toast--info {
  border-left: 3px solid var(--rs-info);
}

/* --- Alert --- */
.rs-alert {
  padding: var(--rs-space-4);
  border-radius: var(--rs-radius-md);
  border-left: 3px solid;
  margin-bottom: var(--rs-space-4);
  font-size: var(--rs-font-size-sm);
}

.rs-alert--success {
  background: rgba(34, 197, 94, 0.1);
  border-color: var(--rs-success);
  color: var(--rs-success);
}

.rs-alert--error {
  background: rgba(239, 68, 68, 0.1);
  border-color: var(--rs-error);
  color: var(--rs-error);
}

.rs-alert--warning {
  background: rgba(245, 158, 11, 0.08);
  border-color: var(--rs-warning);
  color: var(--rs-warning);
}

.rs-alert--info {
  background: rgba(59, 130, 246, 0.1);
  border-color: var(--rs-info);
  color: var(--rs-info);
}

/* --- Badge --- */
.rs-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 2px 8px;
  font-size: var(--rs-font-size-xs);
  font-weight: var(--rs-font-medium);
  line-height: 1.5;
  border-radius: var(--rs-radius-sm);
  white-space: nowrap;
}

.rs-badge--primary {
  background: var(--rs-accent-muted);
  color: var(--rs-accent-primary);
}

.rs-badge--success {
  background: rgba(34, 197, 94, 0.15);
  color: var(--rs-success);
}

.rs-badge--error {
  background: rgba(239, 68, 68, 0.15);
  color: var(--rs-error);
}

.rs-badge--warning {
  background: rgba(245, 158, 11, 0.12);
  color: var(--rs-warning);
}

.rs-badge--neutral {
  background: var(--rs-surface-2);
  color: var(--rs-text-secondary);
}

.rs-badge--pill {
  border-radius: var(--rs-radius-full);
  padding: 2px 12px;
}

/* --- Progress Bar --- */
.rs-progress {
  width: 100%;
  height: 8px;
  background: var(--rs-surface-2);
  border-radius: var(--rs-radius-full);
  overflow: hidden;
}

.rs-progress__bar {
  height: 100%;
  background: var(--rs-accent-primary);
  border-radius: var(--rs-radius-full);
  transition: width var(--rs-transition-normal);
}

.rs-progress__bar--success {
  background: var(--rs-success);
}

.rs-progress__bar--warning {
  background: var(--rs-warning);
}

.rs-progress__bar--error {
  background: var(--rs-error);
}

/* --- Skeleton Loading --- */
.rs-skeleton {
  background: var(--rs-surface-2);
  border-radius: var(--rs-radius-md);
  animation: rs-skeleton-pulse 1.5s ease-in-out infinite;
}

.rs-skeleton--text {
  height: 1em;
  width: 100%;
  margin-bottom: var(--rs-space-2);
}

.rs-skeleton--heading {
  height: 1.5em;
  width: 60%;
  margin-bottom: var(--rs-space-4);
}

.rs-skeleton--avatar {
  width: 40px;
  height: 40px;
  border-radius: var(--rs-radius-full);
}

.rs-skeleton--card {
  height: 160px;
  width: 100%;
}

/* --- Table --- */
.rs-table {
  width: 100%;
  font-size: var(--rs-font-size-sm);
  border-collapse: collapse;
}

.rs-table th {
  text-align: left;
  font-weight: var(--rs-font-semibold);
  color: var(--rs-text-secondary);
  padding: var(--rs-space-3) var(--rs-space-4);
  border-bottom: 2px solid var(--rs-border-default);
}

.rs-table td {
  padding: var(--rs-space-3) var(--rs-space-4);
  border-bottom: 1px solid var(--rs-border-subtle);
  color: var(--rs-text-primary);
}

.rs-table tr:hover td {
  background: var(--rs-surface-1);
}

/* ==========================================================================
   7. TEACHER OVERLAY BASE
   ========================================================================== */

.rs-overlay {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: 56px;
  padding: 0 var(--rs-space-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--rs-space-2);
  z-index: var(--rs-z-overlay);
  background: var(--rs-overlay-bg);
  border-top: 1px solid var(--rs-border-subtle);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  animation: rs-overlay-enter 200ms ease-out;
  transition: opacity 200ms ease, transform 200ms ease;
}

.rs-overlay--hidden {
  opacity: 0;
  transform: translateY(8px);
  pointer-events: none;
}

.rs-overlay-group {
  display: flex;
  align-items: center;
  gap: var(--rs-space-2);
}

.rs-overlay-btn {
  width: 40px;
  height: 40px;
  padding: 8px;
  border-radius: var(--rs-radius-md);
  border: 1px solid var(--rs-border-subtle);
  background: transparent;
  color: var(--rs-text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color var(--rs-transition-fast),
              background var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              transform 80ms ease-in;
  position: relative;
  z-index: var(--rs-z-overlay-tools);
}

.rs-overlay-btn:hover {
  color: var(--rs-text-primary);
  background: var(--rs-surface-2);
  border-color: var(--rs-border-default);
}

.rs-overlay-btn:active {
  transform: scale(0.95);
}

.rs-overlay-btn--active {
  color: var(--rs-accent-primary);
  background: var(--rs-accent-muted);
  border-color: var(--rs-accent-primary);
}

.rs-overlay-btn--active:hover {
  background: var(--rs-accent-muted);
  filter: brightness(1.1);
}

.rs-overlay-btn--disabled {
  opacity: 0.3;
  pointer-events: none;
}

.rs-overlay-separator {
  width: 1px;
  height: 24px;
  background: var(--rs-border-subtle);
  margin: 0 var(--rs-space-2);
}

/* Student counter in overlay */
.rs-student-counter {
  display: flex;
  align-items: center;
  gap: var(--rs-space-2);
  padding: 4px 12px;
  border-radius: var(--rs-radius-full);
  background: var(--rs-surface-1);
  border: 1px solid var(--rs-border-subtle);
  color: var(--rs-text-secondary);
  font-size: var(--rs-font-size-sm);
  font-variant-numeric: tabular-nums;
  min-width: 56px;
  justify-content: center;
}

/* ==========================================================================
   8. STUDENT VIEW BASE
   ========================================================================== */

.rs-student-content {
  max-width: 72ch;
  margin: 0 auto;
  padding: var(--rs-space-6);
  font-size: var(--rs-font-size-md);
  line-height: var(--rs-leading-relaxed);
}

.rs-sync-indicator {
  display: flex;
  align-items: center;
  gap: var(--rs-space-2);
  padding: var(--rs-space-2) var(--rs-space-4);
  font-size: var(--rs-font-size-sm);
  border-bottom: 1px solid var(--rs-border-subtle);
  background: var(--rs-surface-1);
}

.rs-sync-indicator__dot {
  width: 8px;
  height: 8px;
  border-radius: var(--rs-radius-full);
  background: var(--rs-success);
}

.rs-sync-indicator__dot--reviewing {
  background: var(--rs-warning);
}

.rs-sync-indicator__dot--disconnected {
  background: var(--rs-error);
}

.rs-sync-indicator__text {
  color: var(--rs-text-secondary);
}

.rs-sync-indicator__page {
  margin-left: auto;
  color: var(--rs-text-muted);
}

/* Student nav bar */
.rs-student-nav {
  display: flex;
  align-items: center;
  height: 48px;
  padding: 0 var(--rs-space-4);
  background: var(--rs-bg-secondary);
  border-bottom: 1px solid var(--rs-border-default);
  position: sticky;
  top: 0;
  z-index: var(--rs-z-sticky);
}

.rs-student-nav__logo {
  font-weight: var(--rs-font-bold);
  font-size: var(--rs-font-size-base);
  color: var(--rs-text-primary);
  margin-right: var(--rs-space-4);
}

.rs-student-nav__course {
  font-size: var(--rs-font-size-sm);
  color: var(--rs-text-secondary);
  flex: 1;
}

.rs-student-nav__logout {
  font-size: var(--rs-font-size-sm);
  color: var(--rs-text-muted);
  cursor: pointer;
  transition: color var(--rs-transition-fast);
}

.rs-student-nav__logout:hover {
  color: var(--rs-text-primary);
}

/* ==========================================================================
   9. ICON BASE
   ========================================================================== */

.rs-icon {
  display: inline-block;
  width: 24px;
  height: 24px;
  background-color: currentColor;
  mask-size: contain;
  mask-repeat: no-repeat;
  mask-position: center;
  -webkit-mask-size: contain;
  -webkit-mask-repeat: no-repeat;
  -webkit-mask-position: center;
}

.rs-icon--sm {
  width: 16px;
  height: 16px;
}

.rs-icon--lg {
  width: 32px;
  height: 32px;
}

/* ==========================================================================
   10. KEYFRAME ANIMATIONS
   ========================================================================== */

@keyframes rs-overlay-enter {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes rs-overlay-exit {
  from { opacity: 1; transform: translateY(0); }
  to   { opacity: 0; transform: translateY(8px); }
}

@keyframes rs-pointer-pulse {
  0%, 100% { transform: scale(1); opacity: 1; }
  50%      { transform: scale(1.3); opacity: 0.7; }
}

@keyframes rs-scanline {
  0%   { transform: translateY(-100%); }
  100% { transform: translateY(100vh); }
}

@keyframes rs-glow-pulse {
  0%, 100% { text-shadow: 0 0 10px var(--rs-glow-color, #3b82f6); }
  50%      { text-shadow: 0 0 20px var(--rs-glow-color, #3b82f6), 0 0 40px var(--rs-glow-color, #3b82f6); }
}

@keyframes rs-fade-in {
  from { opacity: 0; }
  to   { opacity: 1; }
}

@keyframes rs-scale-in {
  from { opacity: 0; transform: scale(0.95); }
  to   { opacity: 1; transform: scale(1); }
}

@keyframes rs-slide-in-right {
  from { opacity: 0; transform: translateX(100%); }
  to   { opacity: 1; transform: translateX(0); }
}

@keyframes rs-skeleton-pulse {
  0%   { opacity: 1; }
  50%  { opacity: 0.4; }
  100% { opacity: 1; }
}

@keyframes rs-shake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-3px); }
  40%, 80% { transform: translateX(3px); }
}

/* ==========================================================================
   11. RESPONSIVE BREAKPOINTS
   ========================================================================== */

/* Tablet: 768px - 1279px */
@media (max-width: 1279px) {
  .rs-sidebar-layout__sidebar {
    width: 176px;
    padding: var(--rs-space-5) 0;
  }

  .rs-sidebar-layout__main {
    margin-left: 176px;
    padding: var(--rs-space-5);
  }

  .rs-sidebar-layout__sidebar ul {
    padding: 0 var(--rs-space-2);
  }

  .rs-sidebar-layout__sidebar hr {
    margin: var(--rs-space-3) var(--rs-space-3);
  }

  .rs-sidebar-link {
    min-height: 42px;
    padding: 0 var(--rs-space-3);
    font-size: var(--rs-font-size-xs);
  }

  .rs-grid--3 {
    grid-template-columns: repeat(2, 1fr);
  }

  .rs-grid--4 {
    grid-template-columns: repeat(2, 1fr);
  }

  h1 { font-size: var(--rs-font-size-3xl); }
  h2 { font-size: var(--rs-font-size-2xl); }
}

/* Small Desktop: 1024px */
@media (max-width: 1024px) {
  :root {
    --rs-space-8:  28px;
    --rs-space-10: 36px;
    --rs-space-12: 40px;
    --rs-space-16: 52px;
  }

  .rs-course-create-form__actions {
    justify-content: flex-start;
  }
}

/* Mobile: <= 767px */
@media (max-width: 767px) {
  .rs-sidebar-layout__sidebar {
    display: none;
  }

  .rs-sidebar-layout__main {
    margin-left: 0;
    padding: var(--rs-space-4);
    padding-bottom: calc(var(--rs-space-10) + 92px + env(safe-area-inset-bottom));
  }

  .rs-container {
    padding-left: var(--rs-space-4);
    padding-right: var(--rs-space-4);
  }

  .rs-grid--2,
  .rs-grid--3,
  .rs-grid--4 {
    grid-template-columns: 1fr;
  }

  .rs-course-create-form {
    grid-template-columns: 1fr;
  }

  .rs-course-create-form__row {
    grid-template-columns: 1fr;
  }

  .rs-course-create-form__actions {
    justify-content: stretch;
  }

  .rs-course-create-form__actions .rs-btn {
    width: 100%;
  }

  .rs-switch-card {
    min-height: 64px;
    padding: var(--rs-space-3) var(--rs-space-4);
    column-gap: var(--rs-space-4);
  }

  .rs-assignment-option {
    min-height: 60px;
    padding: var(--rs-space-3) var(--rs-space-4);
    gap: var(--rs-space-3);
  }

  .rs-course-lessons-grid {
    grid-template-columns: 1fr;
  }

  .rs-course-assignment-actions .rs-btn {
    width: 100%;
  }

  h1 { font-size: var(--rs-font-size-2xl); }
  h2 { font-size: var(--rs-font-size-xl); }
  h3 { font-size: var(--rs-font-size-lg); }

  .rs-overlay {
    height: 48px;
  }

  #theme-form {
    scroll-margin-top: var(--rs-space-4);
  }

  .rs-theme-selector__grid {
    gap: var(--rs-space-3) !important;
  }

  .rs-theme-card {
    min-height: auto;
    padding: var(--rs-space-3);
  }

  .rs-theme-card .rs-theme-thumb {
    height: 78px !important;
    margin-bottom: var(--rs-space-2) !important;
  }

  .rs-theme-card__meta {
    align-items: flex-start !important;
  }

  .rs-theme-card__modes {
    justify-content: flex-start !important;
    flex-wrap: wrap;
  }

  .rs-theme-card__modes .rs-btn {
    height: 28px !important;
    padding: 0 var(--rs-space-2) !important;
  }

  .rs-theme-selector__preview-card {
    height: 220px !important;
  }

  .rs-dashboard-header {
    flex-wrap: wrap;
    gap: var(--rs-space-3);
    align-items: flex-start !important;
  }

  .rs-dashboard-tools {
    width: 100%;
    justify-content: flex-start;
  }

  .rs-dashboard-room-actions {
    flex-wrap: wrap;
  }

  .rs-dashboard-room-actions > .rs-btn,
  .rs-dashboard-room-actions__form,
  .rs-dashboard-room-actions__form > .rs-btn {
    width: 100%;
    min-width: 0 !important;
  }

  .rs-student-tabs {
    flex-wrap: wrap;
    gap: var(--rs-space-2);
  }

  .rs-student-tabs .rs-btn {
    flex: 1 1 calc(50% - var(--rs-space-2));
    min-width: 0;
    justify-content: center;
  }

  .rs-table {
    display: block;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .rs-table th,
  .rs-table td {
    white-space: nowrap;
  }

  .rs-student-content {
    padding: var(--rs-space-3);
    font-size: var(--rs-font-size-base);
  }

  .rs-modal {
    max-width: 100%;
    padding: var(--rs-space-6);
    border-radius: var(--rs-radius-md);
  }
}

/* ==========================================================================
   12. THEME BACKGROUNDS
   ========================================================================== */

.rs-theme-background {
  position: fixed;
  inset: 0;
  z-index: var(--rs-z-base);
  overflow: hidden;
  pointer-events: none;
}

.rs-three-canvas,
.rs-bg-fallback {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.rs-three-canvas {
  z-index: var(--rs-z-three);
}

.rs-bg-fallback {
  z-index: calc(var(--rs-z-three) - 1);
  opacity: 0;
  transition: opacity var(--rs-transition-normal);
}

.rs-bg-fallback--visible {
  opacity: 1;
}

.rs-bg-fallback--animated {
  animation: rs-bg-drift 18s ease-in-out infinite alternate;
  background-size: 130% 130%;
}

.rs-3d-toggle {
  position: fixed;
  bottom: var(--rs-space-4);
  right: var(--rs-space-4);
  width: 36px;
  height: 36px;
  border-radius: var(--rs-radius-md);
  z-index: var(--rs-z-sticky);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--rs-transition-fast);
  pointer-events: auto;
}

.rs-3d-toggle svg {
  width: 18px;
  height: 18px;
}

html[data-rs-theme="3d"] body {
  background-color: transparent;
}

html[data-rs-theme="3d"] body > *:not(#rs-theme-background):not(.sr-only) {
  position: relative;
  z-index: var(--rs-z-content);
}

:root[data-rs-theme="3d"] .rs-3d-toggle {
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.1);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  color: var(--rs-text-secondary);
}

:root[data-rs-theme="3d"] .rs-3d-toggle:hover {
  background: rgba(255, 255, 255, 0.14);
  color: var(--rs-text-primary);
}

:root[data-rs-theme="3d"] .rs-3d-toggle[aria-pressed="true"] {
  color: var(--rs-accent-primary);
  border-color: var(--rs-border-accent);
}

@keyframes rs-bg-drift {
  0% {
    transform: scale(1) translate3d(0, 0, 0);
  }

  100% {
    transform: scale(1.06) translate3d(-1%, 1%, 0);
  }
}

/* ==========================================================================
   12. ACCESSIBILITY
   ========================================================================== */

/* Focus-visible for keyboard navigation */
:focus-visible {
  outline: 2px solid var(--rs-accent-primary);
  outline-offset: 2px;
}

/* Remove outline for mouse/touch */
:focus:not(:focus-visible) {
  outline: none;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  .rs-scanline,
  .rs-scanline-beam {
    display: none;
  }

  .rs-three-canvas {
    display: none;
  }

  .rs-bg-fallback--animated {
    animation: none;
  }

  .rs-grid-perspective {
    animation: none;
  }

  .rs-overlay {
    animation: none;
  }

  .rs-pointer-indicator {
    animation: none;
  }
}

/* High contrast mode */
@media (prefers-contrast: high) {
  :root {
    --rs-border-default: #888888;
    --rs-border-subtle:  #666666;
    --rs-border-strong:  #ffffff;
    --rs-text-muted:     #aaaaaa;
  }

  .rs-btn--primary {
    border-width: 2px;
  }

  .rs-card {
    border-width: 2px;
  }

  input,
  select,
  textarea {
    border-width: 2px;
  }
}

/* ==========================================================================
   13. PRINT STYLES
   ========================================================================== */

@media print {
  *,
  *::before,
  *::after {
    background: transparent !important;
    color: #000 !important;
    box-shadow: none !important;
    text-shadow: none !important;
  }

  body {
    font-size: 12pt;
    line-height: 1.5;
  }

  .rs-sidebar-layout__sidebar,
  .rs-overlay,
  .rs-toast-container,
  .rs-modal-backdrop,
  .rs-student-nav,
  .rs-sync-indicator,
  .rs-btn,
  .rs-scanline,
  .rs-three-canvas,
  .rs-bg-fallback {
    display: none !important;
  }

  .rs-sidebar-layout__main {
    margin-left: 0 !important;
  }

  a[href]::after {
    content: " (" attr(href) ")";
    font-size: 0.8em;
  }

  h1, h2, h3, h4, h5, h6 {
    page-break-after: avoid;
  }

  img, pre, table {
    page-break-inside: avoid;
  }

  .rs-card {
    border: 1px solid #ccc !important;
    page-break-inside: avoid;
  }
}

/* ==========================================================================
   14. UTILITY CLASSES
   ========================================================================== */

/* Screen reader only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.sr-only:focus,
.sr-only:active {
  width: auto;
  height: auto;
  margin: 0;
  overflow: visible;
  clip: auto;
  white-space: normal;
  left: var(--rs-space-4);
  top: var(--rs-space-4);
  padding: var(--rs-space-3) var(--rs-space-4);
  border-radius: var(--rs-radius-md);
  background: var(--rs-accent-primary);
  color: var(--rs-text-inverse);
  z-index: var(--rs-z-toast);
  box-shadow: var(--rs-shadow-md);
}

/* Hidden */
.rs-hidden {
  display: none !important;
}

.rs-file-trigger {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.rs-file-trigger__label {
  pointer-events: none;
}

.rs-file-trigger__input {
  position: absolute;
  inset: 0;
  display: block;
  width: 100%;
  height: 100%;
  opacity: 0;
  z-index: 1;
  cursor: pointer;
  font-size: 0;
  appearance: none;
  -webkit-appearance: none;
  background: transparent;
}

.rs-invisible {
  visibility: hidden;
}

/* Text alignment */
.rs-text-center { text-align: center; }
.rs-text-left   { text-align: left; }
.rs-text-right  { text-align: right; }

/* Text color utilities */
.rs-text-primary   { color: var(--rs-text-primary); }
.rs-text-secondary { color: var(--rs-text-secondary); }
.rs-text-muted     { color: var(--rs-text-muted); }
.rs-text-accent    { color: var(--rs-accent-primary); }
.rs-text-success   { color: var(--rs-success); }
.rs-text-error     { color: var(--rs-error); }
.rs-text-warning   { color: var(--rs-warning); }

/* Font weight utilities */
.rs-font-regular  { font-weight: var(--rs-font-regular); }
.rs-font-medium   { font-weight: var(--rs-font-medium); }
.rs-font-semibold { font-weight: var(--rs-font-semibold); }
.rs-font-bold     { font-weight: var(--rs-font-bold); }

/* Spacing utilities */
.rs-mb-0  { margin-bottom: 0; }
.rs-mb-2  { margin-bottom: var(--rs-space-2); }
.rs-mb-4  { margin-bottom: var(--rs-space-4); }
.rs-mb-6  { margin-bottom: var(--rs-space-6); }
.rs-mb-8  { margin-bottom: var(--rs-space-8); }

.rs-mt-0  { margin-top: 0; }
.rs-mt-4  { margin-top: var(--rs-space-4); }
.rs-mt-8  { margin-top: var(--rs-space-8); }

.rs-p-0  { padding: 0; }
.rs-p-4  { padding: var(--rs-space-4); }
.rs-p-6  { padding: var(--rs-space-6); }
.rs-p-8  { padding: var(--rs-space-8); }

/* Width utilities */
.rs-w-full { width: 100%; }
.rs-w-auto { width: auto; }

/* Truncation */
.rs-truncate {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

/* Inactive link (unrevealed content) */
.rs-link--inactive {
  opacity: 0.4;
  cursor: default;
  pointer-events: none;
  text-decoration: none;
  color: inherit;
}

/* Pointer indicator */
.rs-pointer-indicator {
  position: fixed;
  width: 20px;
  height: 20px;
  border-radius: var(--rs-radius-full);
  background: var(--rs-accent-primary);
  opacity: 0.85;
  z-index: var(--rs-z-pointer);
  transform: translate(-50%, -50%);
  pointer-events: none;
  animation: rs-pointer-pulse 2s ease-in-out infinite;
  transition: left 100ms linear, top 100ms linear;
}

.rs-pointer-indicator--idle {
  opacity: 0 !important;
  animation: none;
  transition: opacity 500ms ease;
}

/* Spotlight mask */
.rs-spotlight-mask {
  position: fixed;
  inset: 0;
  z-index: var(--rs-z-spotlight);
  pointer-events: none;
  background: radial-gradient(
    circle 120px at var(--rs-spotlight-x, 50%) var(--rs-spotlight-y, 50%),
    transparent 0%,
    transparent 80%,
    rgba(0, 0, 0, 0.7) 100%
  );
}

/* Tabular numbers for counters */
.rs-tabular-nums {
  font-variant-numeric: tabular-nums;
}

/* Password strength bar */
.rs-password-strength {
  width: 200px;
  height: 4px;
  background: var(--rs-surface-2);
  border-radius: var(--rs-radius-full);
  overflow: hidden;
  margin-top: var(--rs-space-1);
}

.rs-password-strength__bar {
  height: 100%;
  border-radius: var(--rs-radius-full);
  transition: width var(--rs-transition-fast), background var(--rs-transition-fast);
}

/* Drop zone for file uploads */
.rs-dropzone {
  border: 2px dashed var(--rs-border-default);
  border-radius: var(--rs-radius-lg);
  padding: var(--rs-space-10);
  text-align: center;
  transition: border-color var(--rs-transition-fast),
              background var(--rs-transition-fast);
  cursor: pointer;
}

.rs-dropzone:hover,
.rs-dropzone--active {
  border-color: var(--rs-accent-primary);
  background: var(--rs-accent-muted);
}

/* Step indicator (wizard) */
.rs-steps {
  display: flex;
  align-items: center;
  gap: var(--rs-space-2);
}

.rs-steps__dot {
  width: 8px;
  height: 8px;
  border-radius: var(--rs-radius-full);
  background: var(--rs-text-muted);
}

.rs-steps__dot--active {
  background: var(--rs-accent-primary);
}

.rs-steps__dot--completed {
  background: var(--rs-success);
}

/* Glass panel base (used by 3D theme) */
.rs-glass {
  backdrop-filter: blur(var(--rs-glass-blur, 16px));
  -webkit-backdrop-filter: blur(var(--rs-glass-blur, 16px));
  background: var(--rs-glass-bg, rgba(255, 255, 255, 0.06));
  border: var(--rs-glass-border, 1px solid rgba(255, 255, 255, 0.12));
  border-radius: var(--rs-radius-lg);
  box-shadow: var(--rs-glass-shadow, 0 8px 32px rgba(0, 0, 0, 0.3));
}

/* Mobile bottom nav */
.rs-bottom-nav {
  display: none;
  position: fixed;
  bottom: max(12px, env(safe-area-inset-bottom));
  left: 50%;
  transform: translateX(-50%);
  width: auto;
  max-width: calc(100% - 24px);
  min-height: 56px;
  background: var(--rs-surface-1);
  border: 1px solid var(--rs-border-default);
  border-color: color-mix(in srgb, var(--rs-border-default) 88%, transparent);
  border-radius: 999px;
  box-shadow: var(--rs-shadow-lg);
  z-index: var(--rs-z-sticky);
  align-items: center;
  justify-content: center;
  gap: 2px;
  padding: 6px;
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  opacity: 1;
  transition: opacity var(--rs-transition-fast),
              background var(--rs-transition-fast),
              border-color var(--rs-transition-fast),
              transform var(--rs-transition-fast);
}

@media (max-width: 767px) {
  .rs-bottom-nav {
    display: flex;
  }
}

.rs-bottom-nav:hover,
.rs-bottom-nav:focus-within {
  opacity: 1;
  transform: translateX(-50%) translateY(-1px);
}

.rs-bottom-nav__item {
  display: flex;
  align-items: center;
  justify-content: center;
  flex: 0 0 auto;
  width: 42px;
  height: 42px;
  padding: 0;
  border-radius: 999px;
  font-size: var(--rs-font-size-xs);
  color: var(--rs-text-muted);
  text-decoration: none;
  transition: color var(--rs-transition-fast),
              background var(--rs-transition-fast),
              transform var(--rs-transition-fast),
              box-shadow var(--rs-transition-fast);
}

.rs-bottom-nav__icon {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  fill: none;
  stroke-width: 1.8;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.rs-bottom-nav__item:hover {
  background: var(--rs-surface-1);
  color: var(--rs-text-primary);
}

.rs-bottom-nav__item--active {
  color: var(--rs-accent-primary);
  background: var(--rs-accent-muted);
  box-shadow: 0 10px 24px rgba(0, 0, 0, 0.18);
}

.rs-bottom-nav__item:focus-visible {
  outline: 2px solid var(--rs-accent-primary);
  outline-offset: 2px;
}