/**
 * Browser Talk Design System Tokens (tokens.css)
 *
 * Authoritative CSS variables, typography, elevation, components, and responsive rules
 * for browser.talk (Marketing Website) and app.browser.talk (Customer Dashboard).
 *
 * Strictly anchored in:
 * - browsertalk/docs/DESIGN.md
 * - /tmp/mission-bt-plan-uiux-dashboard.md (Section 2)
 */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500;600&display=swap');

:root {
  /* ==========================================================================
     1. COLOR PALETTE
     ========================================================================== */

  /* Primary Inks & Grays */
  --bt-color-primary: #0a0a0a;             /* Warm near-black primary CTA */
  --bt-color-primary-active: #1f1f1f;      /* Pressed/active button state */
  --bt-color-primary-disabled: #e5e5e5;    /* Disabled button background */
  --bt-color-ink: #0a0a0a;                 /* Headlines and primary display text */
  --bt-color-body: #3a3a3a;                /* Default running text */
  --bt-color-body-strong: #1a1a1a;         /* Emphasized lead copy */
  --bt-color-muted: #6a6a6a;               /* Secondary text, sub-labels */
  --bt-color-muted-soft: #9a9a9a;          /* Captions, metadata, fine-print */
  --bt-color-hairline: #e5e5e5;            /* 1px border on inputs & quiet cards */
  --bt-color-hairline-soft: #f0f0f0;       /* Subtle dividing rules */

  /* Warm Cream Canvas & Surface System */
  --bt-color-canvas: #fffaf0;              /* Global page background (warm cream) */
  --bt-color-surface-soft: #faf5e8;        /* Nav, footer, hero artifact background */
  --bt-color-surface-card: #f5f0e0;        /* Secondary & testimonial card background */
  --bt-color-surface-strong: #ebe6d6;      /* Emphasized callout surface */
  --bt-color-surface-dark: #0a1a1a;        /* Deep teal-tinted near-black */
  --bt-color-surface-dark-elevated: #1a2a2a; /* Elevated dark card surface */

  /* Contrast Overlays */
  --bt-color-on-primary: #ffffff;          /* Text on dark buttons */
  --bt-color-on-dark: #ffffff;             /* Text on deep teal & pink cards */
  --bt-color-on-dark-soft: #a0a0a0;        /* Secondary text on dark surfaces */

  /* 6-Color Saturated Feature Card Palette & Brand Accents */
  --bt-color-brand-pink: #ff4d8b;          /* Feature Card Pink (outbound / live agent) */
  --bt-color-brand-teal: #1a3a3a;          /* Feature Card Teal (deep teal / featured tier) */
  --bt-color-brand-lavender: #b8a4ed;      /* Feature Card Lavender (agent connectivity) */
  --bt-color-brand-peach: #ffb084;         /* Feature Card Peach (one-click setup) */
  --bt-color-brand-ochre: #e8b94a;         /* Feature Card Ochre (persistence / backups) */
  --bt-color-brand-mint: #a4d4c5;          /* Mint accent for badges & indicators */
  --bt-color-brand-coral: #ff6b5a;         /* Coral accent for warnings & window dots */

  /* Semantic Status Indicators */
  --bt-color-success: #22c55e;             /* Browser Awake / Test Passed */
  --bt-color-warning: #f59e0b;             /* Browser Sleeping / Usage 80% */
  --bt-color-error: #ef4444;               /* Connection Failed / Revoked */
  --bt-color-info: #3b82f6;                /* Informational banner */

  /* Soft Status Tints */
  --bt-color-success-soft: rgba(34, 197, 94, 0.12);
  --bt-color-warning-soft: rgba(245, 158, 11, 0.12);
  --bt-color-error-soft: rgba(239, 68, 68, 0.12);
  --bt-color-info-soft: rgba(59, 130, 246, 0.12);

  /* ==========================================================================
     2. TYPOGRAPHY
     ========================================================================== */

  /* Font Families */
  --bt-font-display: "Plain Black", "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --bt-font-body: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --bt-font-mono: "JetBrains Mono", "SF Mono", "Fira Code", "Menlo", Consolas, monospace;

  /* Display Type (Weight 500 with negative letter-spacing) */
  --bt-type-display-xl-size: 72px;
  --bt-type-display-xl-weight: 500;
  --bt-type-display-xl-line: 1.0;
  --bt-type-display-xl-spacing: -2.5px;

  --bt-type-display-lg-size: 56px;
  --bt-type-display-lg-weight: 500;
  --bt-type-display-lg-line: 1.05;
  --bt-type-display-lg-spacing: -2.0px;

  --bt-type-display-md-size: 40px;
  --bt-type-display-md-weight: 500;
  --bt-type-display-md-line: 1.1;
  --bt-type-display-md-spacing: -1.0px;

  --bt-type-display-sm-size: 32px;
  --bt-type-display-sm-weight: 500;
  --bt-type-display-sm-line: 1.15;
  --bt-type-display-sm-spacing: -0.5px;

  /* Headings & Interface Titles */
  --bt-type-title-lg-size: 24px;
  --bt-type-title-lg-weight: 600;
  --bt-type-title-lg-line: 1.3;
  --bt-type-title-lg-spacing: -0.3px;

  --bt-type-title-md-size: 18px;
  --bt-type-title-md-weight: 600;
  --bt-type-title-md-line: 1.4;
  --bt-type-title-md-spacing: 0;

  --bt-type-title-sm-size: 16px;
  --bt-type-title-sm-weight: 600;
  --bt-type-title-sm-line: 1.4;
  --bt-type-title-sm-spacing: 0;

  /* Body Text */
  --bt-type-body-md-size: 16px;
  --bt-type-body-md-weight: 400;
  --bt-type-body-md-line: 1.55;
  --bt-type-body-md-spacing: 0;

  --bt-type-body-sm-size: 14px;
  --bt-type-body-sm-weight: 400;
  --bt-type-body-sm-line: 1.55;
  --bt-type-body-sm-spacing: 0;

  /* Microcopy, Badges & Interactive */
  --bt-type-caption-size: 13px;
  --bt-type-caption-weight: 500;
  --bt-type-caption-line: 1.4;
  --bt-type-caption-spacing: 0;

  --bt-type-caption-uc-size: 12px;
  --bt-type-caption-uc-weight: 600;
  --bt-type-caption-uc-line: 1.4;
  --bt-type-caption-uc-spacing: 1.5px;

  --bt-type-button-size: 14px;
  --bt-type-button-weight: 600;
  --bt-type-button-line: 1.0;
  --bt-type-button-spacing: 0;

  --bt-type-nav-size: 14px;
  --bt-type-nav-weight: 500;
  --bt-type-nav-line: 1.4;
  --bt-type-nav-spacing: 0;

  /* ==========================================================================
     3. SPACING & LAYOUT RHYTHM (Base 4px)
     ========================================================================== */
  --bt-spacing-xxs: 4px;
  --bt-spacing-xs: 8px;
  --bt-spacing-sm: 12px;
  --bt-spacing-md: 16px;
  --bt-spacing-lg: 24px;
  --bt-spacing-xl: 32px;
  --bt-spacing-xxl: 48px;
  --bt-spacing-xxxl: 64px;
  --bt-spacing-section: 96px;              /* Non-negotiable section rhythm */

  --bt-container-max: 1280px;

  /* ==========================================================================
     4. CORNER RADIUS SCALE
     ========================================================================== */
  --bt-radius-xs: 6px;                    /* Small badges, micro dropdowns */
  --bt-radius-sm: 8px;                    /* Sub-elements, code blocks */
  --bt-radius-md: 12px;                   /* Standard buttons, text inputs (12px per DESIGN.md) */
  --bt-radius-12: 12px;                   /* Design spec 12px alias */
  --bt-radius-lg: 16px;                   /* Content cards, pricing cards */
  --bt-radius-xl: 24px;                   /* Feature cards, hero cards */
  --bt-radius-2xl: 32px;                  /* Large containers, modal shells */
  --bt-radius-pill: 9999px;               /* Badges, category pills, switches */
  --bt-radius-full: 9999px;               /* Circular avatars, icon buttons */

  /* ==========================================================================
     5. ELEVATION & SHADOW SYSTEM (Tactile 3D Shadows & Subtle Drops)
     ========================================================================== */
  --bt-shadow-sm: 0 1px 2px rgba(10, 10, 10, 0.04);
  --bt-shadow-md: 0 4px 12px rgba(10, 10, 10, 0.06);
  --bt-shadow-lg: 0 8px 24px rgba(10, 10, 10, 0.08);
  --bt-shadow-modal: 0 16px 48px rgba(10, 10, 10, 0.12);
  --bt-shadow-window: 0 16px 40px -8px rgba(10, 10, 10, 0.08), 0 4px 12px -2px rgba(10, 10, 10, 0.04);

  /* Tactile 3D Button Shadows */
  --bt-shadow-tactile: 0 2px 0 rgba(10, 10, 10, 0.08), 0 1px 3px rgba(10, 10, 10, 0.06);
  --bt-shadow-tactile-pressed: 0 0 0 rgba(10, 10, 10, 0);

  /* Borders & Focus Rings */
  --bt-border-hairline: 1px solid var(--bt-color-hairline);
  --bt-border-hairline-soft: 1px solid var(--bt-color-hairline-soft);
  --bt-border-dark: 1px solid var(--bt-color-primary);
  --bt-focus-ring: 0 0 0 2px var(--bt-color-canvas), 0 0 0 4px var(--bt-color-primary);

  /* Transitions */
  --bt-transition-fast: 0.15s ease;
  --bt-transition-normal: 0.25s ease;
}

/* ==========================================================================
   GLOBAL CANVAS & BASE RESETS
   ========================================================================== */

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

html {
  font-family: var(--bt-font-body);
  background-color: var(--bt-color-canvas);
  color: var(--bt-color-body);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  margin: 0;
  padding: 0;
  background-color: var(--bt-color-canvas);
  color: var(--bt-color-body);
  font-family: var(--bt-font-body);
}

/* ==========================================================================
   TYPOGRAPHY UTILITIES
   ========================================================================== */

.bt-display-xl {
  font-family: var(--bt-font-display);
  font-size: var(--bt-type-display-xl-size);
  font-weight: var(--bt-type-display-xl-weight);
  line-height: var(--bt-type-display-xl-line);
  letter-spacing: var(--bt-type-display-xl-spacing);
  color: var(--bt-color-ink);
}

.bt-display-lg {
  font-family: var(--bt-font-display);
  font-size: var(--bt-type-display-lg-size);
  font-weight: var(--bt-type-display-lg-weight);
  line-height: var(--bt-type-display-lg-line);
  letter-spacing: var(--bt-type-display-lg-spacing);
  color: var(--bt-color-ink);
}

.bt-display-md {
  font-family: var(--bt-font-display);
  font-size: var(--bt-type-display-md-size);
  font-weight: var(--bt-type-display-md-weight);
  line-height: var(--bt-type-display-md-line);
  letter-spacing: var(--bt-type-display-md-spacing);
  color: var(--bt-color-ink);
}

.bt-display-sm {
  font-family: var(--bt-font-display);
  font-size: var(--bt-type-display-sm-size);
  font-weight: var(--bt-type-display-sm-weight);
  line-height: var(--bt-type-display-sm-line);
  letter-spacing: var(--bt-type-display-sm-spacing);
  color: var(--bt-color-ink);
}

.bt-title-lg {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-title-lg-size);
  font-weight: var(--bt-type-title-lg-weight);
  line-height: var(--bt-type-title-lg-line);
  letter-spacing: var(--bt-type-title-lg-spacing);
  color: var(--bt-color-ink);
}

.bt-title-md {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-title-md-size);
  font-weight: var(--bt-type-title-md-weight);
  line-height: var(--bt-type-title-md-line);
  letter-spacing: var(--bt-type-title-md-spacing);
  color: var(--bt-color-ink);
}

.bt-title-sm {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-title-sm-size);
  font-weight: var(--bt-type-title-sm-weight);
  line-height: var(--bt-type-title-sm-line);
  letter-spacing: var(--bt-type-title-sm-spacing);
  color: var(--bt-color-ink);
}

.bt-body-md {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-body-md-size);
  font-weight: var(--bt-type-body-md-weight);
  line-height: var(--bt-type-body-md-line);
  letter-spacing: var(--bt-type-body-md-spacing);
  color: var(--bt-color-body);
}

.bt-body-sm {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-body-sm-size);
  font-weight: var(--bt-type-body-sm-weight);
  line-height: var(--bt-type-body-sm-line);
  letter-spacing: var(--bt-type-body-sm-spacing);
  color: var(--bt-color-body);
}

.bt-caption {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-caption-size);
  font-weight: var(--bt-type-caption-weight);
  line-height: var(--bt-type-caption-line);
  letter-spacing: var(--bt-type-caption-spacing);
  color: var(--bt-color-muted);
}

.bt-caption-uc {
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-caption-uc-size);
  font-weight: var(--bt-type-caption-uc-weight);
  line-height: var(--bt-type-caption-uc-line);
  letter-spacing: var(--bt-type-caption-uc-spacing);
  text-transform: uppercase;
  color: var(--bt-color-muted);
}

.bt-mono {
  font-family: var(--bt-font-mono);
}

/* ==========================================================================
   BUTTON COMPONENTS
   ========================================================================== */

.bt-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--bt-spacing-xs);
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-button-size);
  font-weight: var(--bt-type-button-weight);
  line-height: var(--bt-type-button-line);
  height: 44px;
  padding: 0 20px;
  border-radius: var(--bt-radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
  user-select: none;
  box-shadow: var(--bt-shadow-tactile);
  transition: background-color var(--bt-transition-fast),
              border-color var(--bt-transition-fast),
              color var(--bt-transition-fast),
              transform 0.1s ease,
              box-shadow var(--bt-transition-fast);
}

.bt-btn:focus-visible {
  outline: none;
  box-shadow: var(--bt-focus-ring);
}

/* Primary Button (Dark near-black) */
.bt-btn-primary {
  background-color: var(--bt-color-primary);
  color: var(--bt-color-on-primary);
  border-color: var(--bt-color-primary);
}

.bt-btn-primary:hover {
  background-color: var(--bt-color-primary-active);
  border-color: var(--bt-color-primary-active);
}

.bt-btn-primary:active {
  transform: translateY(1px);
  box-shadow: var(--bt-shadow-tactile-pressed);
}

/* Secondary Button (Cream with hairline outline) */
.bt-btn-secondary {
  background-color: var(--bt-color-canvas);
  color: var(--bt-color-ink);
  border-color: var(--bt-color-hairline);
}

.bt-btn-secondary:hover {
  background-color: var(--bt-color-surface-soft);
  border-color: var(--bt-color-muted-soft);
}

.bt-btn-secondary:active {
  transform: translateY(1px);
  box-shadow: var(--bt-shadow-tactile-pressed);
}

/* Ghost Button (Transparent background) */
.bt-btn-ghost {
  background-color: transparent;
  color: var(--bt-color-ink);
  border-color: transparent;
  box-shadow: none;
}

.bt-btn-ghost:hover {
  background-color: var(--bt-color-surface-soft);
}

.bt-btn-ghost:active {
  transform: translateY(1px);
}

/* On-Color Button (White background for saturated cards) */
.bt-btn-on-color {
  background-color: #ffffff;
  color: var(--bt-color-ink);
  border-color: rgba(10, 10, 10, 0.08);
}

.bt-btn-on-color:hover {
  background-color: var(--bt-color-surface-soft);
}

.bt-btn-on-color:active {
  transform: translateY(1px);
  box-shadow: var(--bt-shadow-tactile-pressed);
}

/* Button Sizes */
.bt-btn-sm {
  height: 36px;
  padding: 0 14px;
  font-size: 13px;
  border-radius: var(--bt-radius-sm);
}

.bt-btn-lg {
  height: 52px;
  padding: 0 28px;
  font-size: 16px;
  border-radius: var(--bt-radius-md);
}

/* Disabled State */
.bt-btn:disabled,
.bt-btn[disabled],
.bt-btn.is-disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
  box-shadow: none;
}

/* ==========================================================================
   BROWSER MOCK WINDOW WRAPPER (.bt-window)
   ========================================================================== */

.bt-window {
  border-radius: var(--bt-radius-xl);
  border: 1px solid var(--bt-color-hairline);
  background-color: var(--bt-color-canvas);
  box-shadow: var(--bt-shadow-window);
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.bt-window-bar {
  height: 42px;
  background-color: var(--bt-color-surface-soft);
  border-bottom: 1px solid var(--bt-color-hairline);
  display: flex;
  align-items: center;
  padding: 0 var(--bt-spacing-md);
  gap: var(--bt-spacing-sm);
}

.bt-window-dots {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.bt-window-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  display: inline-block;
}

/* Window dot candy colors */
.bt-window-dot:nth-child(1),
.bt-window-dot-coral,
.bt-window-dot-red {
  background-color: var(--bt-color-brand-coral);
}

.bt-window-dot:nth-child(2),
.bt-window-dot-ochre,
.bt-window-dot-yellow {
  background-color: var(--bt-color-brand-ochre);
}

.bt-window-dot:nth-child(3),
.bt-window-dot-mint,
.bt-window-dot-green {
  background-color: var(--bt-color-brand-mint);
}

.bt-window-address {
  flex: 1;
  max-width: 480px;
  margin: 0 auto;
  height: 26px;
  background-color: var(--bt-color-canvas);
  border: 1px solid var(--bt-color-hairline-soft);
  border-radius: var(--bt-radius-pill);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--bt-font-mono);
  font-size: 12px;
  color: var(--bt-color-muted);
  padding: 0 var(--bt-spacing-sm);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.bt-window-content {
  position: relative;
  flex: 1;
  min-height: 200px;
  background-color: var(--bt-color-canvas);
}

/* ==========================================================================
   FEATURE CARD PALETTE & CARD RHYTHM
   ========================================================================== */

.bt-card {
  border-radius: var(--bt-radius-xl);
  padding: var(--bt-spacing-xl);
  background-color: var(--bt-color-surface-card);
  border: 1px solid var(--bt-color-hairline);
  position: relative;
  overflow: hidden;
}

/* 6 Saturated Brand Card Surfaces */
.bt-card-pink {
  background-color: var(--bt-color-brand-pink);
  color: var(--bt-color-on-dark);
  border: none;
}

.bt-card-pink h1, .bt-card-pink h2, .bt-card-pink h3, .bt-card-pink h4,
.bt-card-pink .bt-title-lg, .bt-card-pink .bt-title-md, .bt-card-pink .bt-title-sm,
.bt-card-pink p, .bt-card-pink .bt-body-md, .bt-card-pink .bt-body-sm {
  color: var(--bt-color-on-dark);
}

.bt-card-teal {
  background-color: var(--bt-color-brand-teal);
  color: var(--bt-color-on-dark);
  border: none;
}

.bt-card-teal h1, .bt-card-teal h2, .bt-card-teal h3, .bt-card-teal h4,
.bt-card-teal .bt-title-lg, .bt-card-teal .bt-title-md, .bt-card-teal .bt-title-sm,
.bt-card-teal p, .bt-card-teal .bt-body-md, .bt-card-teal .bt-body-sm {
  color: var(--bt-color-on-dark);
}

.bt-card-lavender {
  background-color: var(--bt-color-brand-lavender);
  color: var(--bt-color-ink);
  border: none;
}

.bt-card-peach {
  background-color: var(--bt-color-brand-peach);
  color: var(--bt-color-ink);
  border: none;
}

.bt-card-ochre {
  background-color: var(--bt-color-brand-ochre);
  color: var(--bt-color-ink);
  border: none;
}

.bt-card-cream {
  background-color: var(--bt-color-surface-card);
  color: var(--bt-color-ink);
  border: 1px solid var(--bt-color-hairline);
}

.bt-card-soft {
  background-color: var(--bt-color-surface-soft);
  color: var(--bt-color-ink);
  border: 1px solid var(--bt-color-hairline);
}

/* ==========================================================================
   STATUS INDICATORS & BADGES
   ========================================================================== */

.bt-badge,
.bt-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 12px;
  border-radius: var(--bt-radius-pill);
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-caption-size);
  font-weight: 500;
  line-height: 1.4;
  white-space: nowrap;
}

.bt-badge-awake,
.bt-status-awake {
  background-color: var(--bt-color-success-soft);
  color: #15803d;
  border: 1px solid rgba(34, 197, 94, 0.25);
}

.bt-badge-sleeping,
.bt-status-sleeping {
  background-color: var(--bt-color-warning-soft);
  color: #b45309;
  border: 1px solid rgba(245, 158, 11, 0.25);
}

.bt-badge-starting,
.bt-status-starting {
  background-color: rgba(184, 164, 237, 0.2);
  color: #5b21b6;
  border: 1px solid rgba(184, 164, 237, 0.35);
}

.bt-badge-error,
.bt-status-error {
  background-color: var(--bt-color-error-soft);
  color: #b91c1c;
  border: 1px solid rgba(239, 68, 68, 0.25);
}

.bt-badge-neutral {
  background-color: var(--bt-color-surface-card);
  color: var(--bt-color-ink);
  border: 1px solid var(--bt-color-hairline);
}

/* Status Dot with Optional Pulse */
.bt-status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
  flex-shrink: 0;
}

.bt-status-dot-awake {
  background-color: var(--bt-color-success);
}

.bt-status-dot-sleeping {
  background-color: var(--bt-color-warning);
}

.bt-status-dot-starting {
  background-color: var(--bt-color-brand-lavender);
}

.bt-status-dot-error {
  background-color: var(--bt-color-error);
}

@keyframes bt-pulse {
  0%, 100% {
    opacity: 1;
    transform: scale(1);
  }
  50% {
    opacity: 0.45;
    transform: scale(1.25);
  }
}

.bt-status-dot-pulse {
  animation: bt-pulse 2s infinite ease-in-out;
}

/* ==========================================================================
   INPUTS & FORM CONTROLS
   ========================================================================== */

.bt-label {
  display: block;
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-caption-size);
  font-weight: 500;
  color: var(--bt-color-ink);
  margin-bottom: var(--bt-spacing-xxs);
}

.bt-input {
  display: block;
  width: 100%;
  height: 44px;
  padding: 0 var(--bt-spacing-md);
  background-color: var(--bt-color-canvas);
  color: var(--bt-color-ink);
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-body-md-size);
  border: 1px solid var(--bt-color-hairline);
  border-radius: var(--bt-radius-md);
  transition: border-color var(--bt-transition-fast), box-shadow var(--bt-transition-fast);
}

.bt-input:focus {
  outline: none;
  border-color: var(--bt-color-primary);
  box-shadow: var(--bt-focus-ring);
}

.bt-input::placeholder {
  color: var(--bt-color-muted-soft);
}

.bt-select {
  display: block;
  width: 100%;
  height: 44px;
  padding: 0 var(--bt-spacing-md);
  background-color: var(--bt-color-canvas);
  color: var(--bt-color-ink);
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-body-md-size);
  border: 1px solid var(--bt-color-hairline);
  border-radius: var(--bt-radius-md);
  cursor: pointer;
  transition: border-color var(--bt-transition-fast), box-shadow var(--bt-transition-fast);
}

.bt-select:focus {
  outline: none;
  border-color: var(--bt-color-primary);
  box-shadow: var(--bt-focus-ring);
}

/* ==========================================================================
   TABS & NAVIGATION HELPERS
   ========================================================================== */

.bt-tabs {
  display: inline-flex;
  gap: var(--bt-spacing-xxs);
  background-color: var(--bt-color-surface-soft);
  padding: 4px;
  border-radius: var(--bt-radius-pill);
  border: 1px solid var(--bt-color-hairline-soft);
}

.bt-tab {
  padding: 8px 16px;
  border-radius: var(--bt-radius-pill);
  font-family: var(--bt-font-body);
  font-size: var(--bt-type-nav-size);
  font-weight: 500;
  color: var(--bt-color-muted);
  background: transparent;
  border: none;
  cursor: pointer;
  transition: background-color var(--bt-transition-fast), color var(--bt-transition-fast);
}

.bt-tab:hover {
  color: var(--bt-color-ink);
}

.bt-tab.is-active,
.bt-tab-active {
  background-color: var(--bt-color-surface-card);
  color: var(--bt-color-ink);
  font-weight: 600;
  box-shadow: var(--bt-shadow-sm);
}

/* ==========================================================================
   CODE BLOCKS
   ========================================================================== */

.bt-code-block {
  background-color: var(--bt-color-surface-dark);
  color: #f0f0f0;
  font-family: var(--bt-font-mono);
  font-size: 13px;
  line-height: 1.6;
  border-radius: var(--bt-radius-lg);
  padding: var(--bt-spacing-md) var(--bt-spacing-lg);
  overflow-x: auto;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.bt-code-inline {
  font-family: var(--bt-font-mono);
  font-size: 0.9em;
  background-color: var(--bt-color-surface-card);
  padding: 2px 6px;
  border-radius: var(--bt-radius-xs);
  border: 1px solid var(--bt-color-hairline);
  color: var(--bt-color-ink);
}

/* ==========================================================================
   CONTAINER & SECTION RHYTHM
   ========================================================================== */

.bt-container {
  max-width: var(--bt-container-max);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--bt-spacing-lg);
  padding-right: var(--bt-spacing-lg);
  width: 100%;
}

.bt-section {
  padding-top: var(--bt-spacing-section);
  padding-bottom: var(--bt-spacing-section);
}

/* Simple Flex & Grid Layouts */
.bt-grid {
  display: grid;
  gap: var(--bt-spacing-xl);
}

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

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

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

.bt-flex {
  display: flex;
}

.bt-flex-col {
  display: flex;
  flex-direction: column;
}

.bt-items-center {
  align-items: center;
}

.bt-justify-between {
  justify-content: space-between;
}

/* ==========================================================================
   RESPONSIVE BREAKPOINTS
   - Mobile:  < 768px (per DESIGN.md:508)
   - Tablet:  768px - 1024px
   - Desktop: > 1024px
   ========================================================================== */

@media (max-width: 1024px) {
  .bt-grid-3 {
    grid-template-columns: repeat(2, 1fr);
  }

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

  .bt-display-xl {
    font-size: 56px;
    letter-spacing: -2.0px;
  }

  .bt-display-lg {
    font-size: 42px;
    letter-spacing: -1.5px;
  }
}

@media (max-width: 768px) {
  .bt-grid-2,
  .bt-grid-3,
  .bt-grid-4 {
    grid-template-columns: 1fr;
  }

  .bt-display-xl {
    font-size: 38px;
    line-height: 1.1;
    letter-spacing: -1.5px;
  }

  .bt-display-lg {
    font-size: 32px;
    line-height: 1.15;
    letter-spacing: -1.0px;
  }

  .bt-display-md {
    font-size: 26px;
    line-height: 1.2;
    letter-spacing: -0.5px;
  }

  .bt-section {
    padding-top: var(--bt-spacing-xxl);
    padding-bottom: var(--bt-spacing-xxl);
  }

  .bt-card {
    padding: var(--bt-spacing-lg);
    border-radius: var(--bt-radius-lg);
  }

  .bt-container {
    padding-left: var(--bt-spacing-md);
    padding-right: var(--bt-spacing-md);
  }
}

/* ==========================================================================
   ACCESSIBILITY
   ========================================================================== */

@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;
  }
}