/* ============================================================
   ChitSheet — Global CSS Design System
   ============================================================ */

/* ---- CSS Variables (Light Mode) ---- */
:root {
  /* Brand Colors */
  --brand-primary: #6C63FF;
  --brand-primary-hover: #5a52e0;
  --brand-secondary: #4ECDC4;
  --brand-accent: #FF6B6B;
  --brand-warning: #FFD93D;
  --brand-success: #6BCB77;

  /* Gradient */
  --gradient-brand: linear-gradient(135deg, #6C63FF 0%, #4ECDC4 100%);
  --gradient-warm: linear-gradient(135deg, #FF6B6B 0%, #FFD93D 100%);
  --gradient-hero: radial-gradient(ellipse at 60% 0%, rgba(108,99,255,0.15) 0%, transparent 60%),
                   radial-gradient(ellipse at 10% 80%, rgba(78,205,196,0.12) 0%, transparent 50%);

  /* Backgrounds */
  --bg-page: #FAFAFA;
  --bg-surface: #FFFFFF;
  --bg-surface-2: #F5F5F7;
  --bg-surface-3: #EFEFEF;
  --bg-overlay: rgba(255,255,255,0.85);
  --bg-glass: rgba(255,255,255,0.7);

  /* Text */
  --text-primary: #0A0A0F;
  --text-secondary: #4A4A5A;
  --text-muted: #8A8A9A;
  --text-placeholder: #B0B0C0;
  --text-on-brand: #FFFFFF;

  /* Borders */
  --border-subtle: rgba(0,0,0,0.06);
  --border-default: rgba(0,0,0,0.10);
  --border-strong: rgba(0,0,0,0.16);
  --border-brand: rgba(108,99,255,0.35);

  /* Shadows */
  --shadow-xs: 0 1px 3px rgba(0,0,0,0.05);
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.07);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.09);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.12);
  --shadow-xl: 0 20px 60px rgba(0,0,0,0.15);
  --shadow-brand: 0 8px 32px rgba(108,99,255,0.28);
  --shadow-glow: 0 0 60px rgba(108,99,255,0.2);

  /* Typography */
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-display: 'Outfit', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  /* Spacing */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;
  --space-20: 80px;
  --space-24: 96px;

  /* Border Radius */
  --radius-xs: 4px;
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-2xl: 32px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4,0,0.2,1);
  --transition-base: 250ms cubic-bezier(0.4,0,0.2,1);
  --transition-slow: 400ms cubic-bezier(0.4,0,0.2,1);
  --transition-spring: 350ms cubic-bezier(0.34,1.56,0.64,1);

  /* Navbar */
  --navbar-height: 64px;
  --navbar-bg: rgba(255,255,255,0.8);

  /* Z-indexes */
  --z-dropdown: 100;
  --z-modal: 200;
  --z-overlay: 300;
  --z-toast: 400;
  --z-tooltip: 500;
}

/* ---- Dark Mode ---- */
[data-theme="dark"] {
  --bg-page: #0A0A0F;
  --bg-surface: #13131A;
  --bg-surface-2: #1A1A24;
  --bg-surface-3: #22222E;
  --bg-overlay: rgba(19,19,26,0.9);
  --bg-glass: rgba(19,19,26,0.75);

  --text-primary: #F0F0F8;
  --text-secondary: #A0A0B8;
  --text-muted: #60607A;
  --text-placeholder: #40404A;

  --border-subtle: rgba(255,255,255,0.04);
  --border-default: rgba(255,255,255,0.08);
  --border-strong: rgba(255,255,255,0.14);
  --border-brand: rgba(108,99,255,0.4);

  --shadow-xs: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.4);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.5);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.6);
  --shadow-xl: 0 20px 60px rgba(0,0,0,0.7);

  --navbar-bg: rgba(10,10,15,0.85);
}

/* ---- Reset & Base ---- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-page);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  transition: background-color var(--transition-base), color var(--transition-base);
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
}

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

a:hover { color: var(--brand-primary-hover); }

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

input, textarea, button, select {
  font-family: var(--font-sans);
  font-size: inherit;
}

/* ---- Container ---- */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-6);
}

/* ---- Buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-lg);
  font-size: 0.9rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  border: none;
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
  white-space: nowrap;
  line-height: 1;
  position: relative;
  overflow: hidden;
}

.btn::after {
  content: '';
  position: absolute;
  inset: 0;
  background: white;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.btn:hover::after { opacity: 0.08; }
.btn:active::after { opacity: 0.15; }

.btn-primary {
  background: var(--gradient-brand);
  color: var(--text-on-brand);
  box-shadow: var(--shadow-brand);
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 12px 40px rgba(108,99,255,0.4);
  color: var(--text-on-brand);
}

.btn-primary:active { transform: translateY(0); }

.btn-secondary {
  background: var(--bg-surface-2);
  color: var(--text-primary);
  border: 1px solid var(--border-default);
}

.btn-secondary:hover {
  background: var(--bg-surface-3);
  color: var(--text-primary);
  transform: translateY(-1px);
}

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
  border: 1px solid var(--border-default);
}

.btn-ghost:hover {
  background: var(--bg-surface-2);
  color: var(--text-primary);
  transform: translateY(-1px);
}

.btn-danger {
  background: rgba(255,100,100,0.1);
  color: #ff4444;
  border: 1px solid rgba(255,100,100,0.2);
}

.btn-danger:hover {
  background: rgba(255,100,100,0.2);
  color: #ff4444;
}

.btn-sm {
  padding: var(--space-2) var(--space-3);
  font-size: 0.8rem;
  border-radius: var(--radius-sm);
}

.btn-lg {
  padding: var(--space-4) var(--space-8);
  font-size: 1rem;
  border-radius: var(--radius-xl);
}

.btn-icon {
  width: 36px;
  height: 36px;
  padding: 0;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
}

/* ---- Navbar ---- */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: var(--z-dropdown);
  height: var(--navbar-height);
  background: var(--navbar-bg);
  backdrop-filter: blur(16px) saturate(180%);
  -webkit-backdrop-filter: blur(16px) saturate(180%);
  border-bottom: 1px solid var(--border-subtle);
  transition: all var(--transition-base);
}

.navbar.scrolled {
  box-shadow: var(--shadow-md);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-6);
  height: 100%;
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--text-primary);
  text-decoration: none;
  flex-shrink: 0;
}

.logo-icon {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  overflow: hidden;
  flex-shrink: 0;
}

.logo-icon.small {
  width: 28px;
  height: 28px;
}

.logo-icon svg { width: 100%; height: 100%; }

.logo-text {
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: var(--gradient-brand);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  flex: 1;
}

.nav-link {
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: all var(--transition-fast);
}

.nav-link:hover, .nav-link.active {
  color: var(--text-primary);
  background: var(--bg-surface-2);
}

.nav-cta { margin-left: auto; }

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-left: auto;
}

.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-sm);
  background: var(--bg-surface-2);
  border: 1px solid var(--border-default);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  background: var(--bg-surface-3);
  transform: scale(1.05);
}

.theme-icon {
  position: absolute;
  transition: all var(--transition-base);
  line-height: 1;
}

.theme-toggle { position: relative; overflow: hidden; }

[data-theme="light"] .theme-icon.moon { opacity: 0; transform: translateY(10px); }
[data-theme="light"] .theme-icon.sun { opacity: 1; transform: translateY(0); }
[data-theme="dark"] .theme-icon.sun { opacity: 0; transform: translateY(-10px); }
[data-theme="dark"] .theme-icon.moon { opacity: 1; transform: translateY(0); }

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-2);
  border-radius: var(--radius-sm);
}

.hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition-base);
}

.hamburger.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.hamburger.active span:nth-child(2) { opacity: 0; transform: scaleX(0); }
.hamburger.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

/* ---- Toast System ---- */
.toast-container {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  z-index: var(--z-toast);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  pointer-events: none;
}

.toast {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background: var(--bg-surface);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-primary);
  pointer-events: all;
  min-width: 240px;
  max-width: 360px;
  animation: toastIn 0.35s var(--transition-spring) forwards;
  backdrop-filter: blur(16px);
}

.toast.removing {
  animation: toastOut 0.25s ease-in forwards;
}

.toast-icon {
  font-size: 1.1rem;
  flex-shrink: 0;
}

.toast-msg { flex: 1; line-height: 1.4; }

.toast-close {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1rem;
  padding: 2px;
  border-radius: 4px;
  display: flex;
  align-items: center;
  pointer-events: all;
  transition: color var(--transition-fast);
}

.toast-close:hover { color: var(--text-primary); }

.toast.success { border-left: 3px solid var(--brand-success); }
.toast.error { border-left: 3px solid var(--brand-accent); }
.toast.warning { border-left: 3px solid var(--brand-warning); }
.toast.info { border-left: 3px solid var(--brand-primary); }

@keyframes toastIn {
  from { transform: translateX(110%); opacity: 0; }
  to   { transform: translateX(0);    opacity: 1; }
}

@keyframes toastOut {
  from { transform: translateX(0);    opacity: 1; }
  to   { transform: translateX(110%); opacity: 0; }
}

/* ---- Modal System ---- */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  backdrop-filter: blur(8px);
  z-index: var(--z-modal);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-4);
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
}

.modal-overlay.open {
  opacity: 1;
  visibility: visible;
}

.modal {
  background: var(--bg-surface);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-2xl);
  box-shadow: var(--shadow-xl);
  padding: var(--space-8);
  width: 100%;
  max-width: 520px;
  transform: scale(0.95) translateY(10px);
  transition: transform var(--transition-spring);
  max-height: 90vh;
  overflow-y: auto;
}

.modal-overlay.open .modal {
  transform: scale(1) translateY(0);
}

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

.modal-title {
  font-size: 1.2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
}

.modal-close {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  background: var(--bg-surface-2);
  border: 1px solid var(--border-default);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  color: var(--text-muted);
  transition: all var(--transition-fast);
}

.modal-close:hover {
  background: var(--bg-surface-3);
  color: var(--text-primary);
}

/* ---- Form Elements ---- */
.form-group {
  margin-bottom: var(--space-4);
}

.form-label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: var(--space-2);
  letter-spacing: 0.01em;
}

.form-input, .form-select, .form-textarea {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  background: var(--bg-surface-2);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.9rem;
  transition: all var(--transition-fast);
  outline: none;
}

.form-input:focus, .form-select:focus, .form-textarea:focus {
  border-color: var(--brand-primary);
  box-shadow: 0 0 0 3px rgba(108,99,255,0.12);
  background: var(--bg-surface);
}

.form-input::placeholder { color: var(--text-placeholder); }

.form-textarea {
  min-height: 120px;
  resize: vertical;
  line-height: 1.6;
}

/* ---- Slider ---- */
.form-range {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 4px;
  background: var(--border-default);
  border-radius: var(--radius-full);
  outline: none;
  cursor: pointer;
}

.form-range::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--brand-primary);
  box-shadow: 0 2px 8px rgba(108,99,255,0.4);
  cursor: pointer;
  transition: transform var(--transition-fast);
}

.form-range::-webkit-slider-thumb:hover { transform: scale(1.2); }

/* ---- Badge / Chip ---- */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  background: var(--bg-surface-2);
  color: var(--text-secondary);
  border: 1px solid var(--border-default);
}

.badge-primary {
  background: rgba(108,99,255,0.12);
  color: var(--brand-primary);
  border-color: rgba(108,99,255,0.2);
}

/* ---- Scrollbar ---- */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: var(--border-strong);
  border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* ---- Selection ---- */
::selection {
  background: rgba(108,99,255,0.2);
  color: var(--text-primary);
}

/* ---- Utility Classes ---- */
.gradient-text {
  background: var(--gradient-brand);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.text-muted { color: var(--text-muted); }
.text-secondary { color: var(--text-secondary); }
.text-center { text-align: center; }

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0);
  white-space: nowrap; border: 0;
}

.hide-mobile { display: block; }

/* ---- Divider ---- */
.divider {
  width: 100%;
  height: 1px;
  background: var(--border-subtle);
  margin: var(--space-6) 0;
}

/* ---- Loading Spinner ---- */
.spinner {
  width: 20px;
  height: 20px;
  border: 2px solid var(--border-default);
  border-top-color: var(--brand-primary);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
}

@keyframes spin { to { transform: rotate(360deg); } }

/* ---- Skeleton Loader ---- */
.skeleton {
  background: linear-gradient(90deg,
    var(--bg-surface-2) 25%,
    var(--bg-surface-3) 50%,
    var(--bg-surface-2) 75%);
  background-size: 200% 100%;
  animation: shimmer 1.5s infinite;
  border-radius: var(--radius-sm);
}

@keyframes shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ---- Keyboard Shortcut ---- */
kbd {
  display: inline-flex;
  align-items: center;
  padding: 2px 6px;
  background: var(--bg-surface-2);
  border: 1px solid var(--border-strong);
  border-bottom-width: 2px;
  border-radius: 5px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-secondary);
  font-weight: 500;
}

/* ---- Tooltip ---- */
[data-tooltip] {
  position: relative;
}

[data-tooltip]::before {
  content: attr(data-tooltip);
  position: absolute;
  bottom: calc(100% + 8px);
  left: 50%;
  transform: translateX(-50%) scale(0.9);
  background: var(--text-primary);
  color: var(--bg-page);
  padding: 5px 10px;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 500;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: all var(--transition-fast);
  z-index: var(--z-tooltip);
}

[data-tooltip]:hover::before {
  opacity: 1;
  transform: translateX(-50%) scale(1);
}

/* ---- Fade Animations ---- */
.fade-in {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ---- Section Shared Styles ---- */
.section-header {
  text-align: center;
  margin-bottom: var(--space-16);
}

.section-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 6px 14px;
  background: rgba(108,99,255,0.08);
  color: var(--brand-primary);
  border: 1px solid rgba(108,99,255,0.2);
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: var(--space-5);
}

.section-title {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1.15;
  margin-bottom: var(--space-4);
}

.section-subtitle {
  font-size: 1.05rem;
  color: var(--text-secondary);
  max-width: 520px;
  margin: 0 auto;
  line-height: 1.7;
}

/* ---- Page Transition ---- */
.page-enter {
  animation: pageEnter 0.4s ease-out;
}

@keyframes pageEnter {
  from { opacity: 0; transform: translateY(8px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ---- Responsive ---- */
@media (max-width: 768px) {
  :root { --navbar-height: 56px; }

  .nav-links {
    display: none;
    position: fixed;
    top: var(--navbar-height);
    left: 0;
    right: 0;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border-default);
    flex-direction: column;
    padding: var(--space-4);
    gap: var(--space-1);
    box-shadow: var(--shadow-lg);
  }

  .nav-links.open { display: flex; }
  .nav-link { width: 100%; }
  .nav-cta { width: 100%; justify-content: center; margin-top: var(--space-2); }
  .hamburger { display: flex; }
  .hide-mobile { display: none; }
  .container { padding: 0 var(--space-4); }
  .toast-container { left: var(--space-4); right: var(--space-4); }
  .toast { max-width: 100%; }
}

@media (max-width: 480px) {
  .btn-lg {
    padding: var(--space-3) var(--space-6);
    font-size: 0.9rem;
  }
}