/**
 * Yao Engine - Global Styles
 *
 * All styles reference variables from variables.css.
 * No hardcoded colors — every color value uses a CSS variable.
 *
 * Structure:
 *   1. Reset
 *   2. Base Elements (html, body, typography, links, media)
 *   3. Layout (.container, .section, .main)
 *   4. Buttons (.btn)
 *   5. Form Controls (.select)
 *   6. Cards (.card)
 *   7. Utilities (text, spacing, flex, grid, sr-only)
 *   8. Scrollbar
 *   9. Animations
 */

/* ========================
 * 1. Reset
 * ======================== */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

/* ========================
 * 2. Base Elements
 * ======================== */
html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-normal);
  line-height: var(--line-height-normal);
  color: var(--color-text);
  background: var(--color-bg-page);
  min-height: 100vh;
  overflow-x: hidden;
  transition:
    background var(--transition-slow),
    color var(--transition-normal);
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-family: var(--font-family-display);
  font-weight: var(--font-weight-bold);
  line-height: var(--line-height-tight);
  color: var(--color-text);
  margin-bottom: var(--spacing-md);
}

h1 {
  font-size: var(--font-size-5xl);
  font-weight: 800;
  letter-spacing: -0.03em;
}
h2 {
  font-size: var(--font-size-4xl);
  letter-spacing: -0.02em;
}
h3 {
  font-size: var(--font-size-3xl);
  letter-spacing: -0.01em;
}
h4 {
  font-size: var(--font-size-2xl);
}
h5 {
  font-size: var(--font-size-xl);
}
h6 {
  font-size: var(--font-size-lg);
}

p {
  margin-bottom: var(--spacing-md);
  color: var(--color-text-secondary);
}

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

a:hover:not(.btn) {
  color: var(--color-primary-hover);
}

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

small {
  font-size: var(--font-size-sm);
}

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

::selection {
  background-color: var(--color-primary);
  color: var(--color-text-inverse);
}

/* ========================
 * 3. Layout
 * ======================== */
.main {
  padding-top: var(--header-height);
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
  position: relative;
}

.container--narrow {
  max-width: var(--max-width-narrow);
}

.container--wide {
  max-width: var(--max-width-wide);
}

.section {
  padding: var(--spacing-5xl) 0;
  position: relative;
}

@media (max-width: 640px) {
  .container {
    padding: 0 var(--spacing-lg);
  }
}

/* ========================
 * 4. Buttons
 *   --primary: brand action (solid primary color)
 *   --secondary: alternative action (outlined)
 *   --ghost: subtle / tertiary action
 *   --sm / --lg: size variants
 * ======================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-medium);
  line-height: 1;
  text-decoration: none;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all var(--transition-normal);
  white-space: nowrap;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn--primary {
  background: var(--color-primary);
  color: #ffffff;
  border-color: var(--color-primary);
}

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

.btn--secondary {
  background: transparent;
  color: var(--color-text);
  border-color: var(--color-border);
}

.btn--secondary:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

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

.btn--ghost:hover {
  color: var(--color-primary);
  background: var(--color-bg-hover);
}

.btn--xs {
  padding: 4px var(--spacing-sm);
  font-size: var(--font-size-xs);
  gap: 4px;
}

.btn--sm {
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: var(--font-size-sm);
}

.btn--lg {
  padding: var(--spacing-lg) var(--spacing-2xl);
  font-size: var(--font-size-lg);
  border-radius: var(--radius-md);
}

/* ========================
 * 5. Form Controls
 *   .select: styled <select> dropdown matching btn appearance
 *   Combine with --sm / --lg for size variants
 * ======================== */
.select {
  display: inline-flex;
  align-items: center;
  position: relative;
  font-size: var(--font-size-base);
  font-weight: var(--font-weight-medium);
  font-family: inherit;
  line-height: 1;
  color: var(--color-text);
  background: var(--color-bg-card-solid);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: var(--spacing-md) var(--spacing-2xl) var(--spacing-md) var(--spacing-md);
  cursor: pointer;
  transition: all var(--transition-normal);
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12' fill='none'%3E%3Cpath d='M2.5 4.5L6 8L9.5 4.5' stroke='%236c757d' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
  background-size: 12px 12px;
  white-space: nowrap;
}

.select:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px rgba(51, 113, 252, 0.15);
}

.select--sm {
  padding: var(--spacing-sm) var(--spacing-xl) var(--spacing-sm) var(--spacing-md);
  font-size: var(--font-size-sm);
}

.select--lg {
  padding: var(--spacing-lg) var(--spacing-3xl) var(--spacing-lg) var(--spacing-xl);
  font-size: var(--font-size-lg);
  border-radius: var(--radius-md);
}

[data-theme="dark"] .select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12' fill='none'%3E%3Cpath d='M2.5 4.5L6 8L9.5 4.5' stroke='%23adb5bd' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
}

/* ========================
 * 6. Cards
 * ======================== */
.card {
  background: var(--color-bg-card-solid);
  border: 1px solid var(--color-border-light);
  border-radius: var(--radius-md);
  padding: var(--spacing-xl);
  transition: all var(--transition-normal);
  box-shadow: var(--shadow-sm);
}

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

.card--clickable {
  cursor: pointer;
}

/* ========================
 * 7. Utilities
 * ======================== */

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

/* Text color */
.text-primary {
  color: var(--color-primary);
}
.text-secondary {
  color: var(--color-text-secondary);
}
.text-muted {
  color: var(--color-text-muted);
}

/* Subtitle phrase gap — replaces punctuation between clauses */
.subtitle-gap {
  display: inline-block;
  width: 0.2em;
}

/* Gradient text (accent decoration) */
.text-gradient {
  background: linear-gradient(
    135deg,
    var(--color-accent-cyan),
    var(--color-accent-purple)
  );
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Flex */
.flex {
  display: flex;
}
.flex--center {
  align-items: center;
  justify-content: center;
}
.flex--between {
  align-items: center;
  justify-content: space-between;
}
.flex--col {
  flex-direction: column;
}
.flex--wrap {
  flex-wrap: wrap;
}

/* Gap */
.gap-sm {
  gap: var(--spacing-sm);
}
.gap-md {
  gap: var(--spacing-md);
}
.gap-lg {
  gap: var(--spacing-lg);
}
.gap-xl {
  gap: var(--spacing-xl);
}

/* Grid */
.grid {
  display: grid;
  gap: var(--spacing-lg);
}
.grid--2 {
  grid-template-columns: repeat(2, 1fr);
}
.grid--3 {
  grid-template-columns: repeat(3, 1fr);
}
.grid--4 {
  grid-template-columns: repeat(4, 1fr);
}

@media (max-width: 1024px) {
  .grid--3,
  .grid--4 {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (max-width: 640px) {
  .grid--2,
  .grid--3,
  .grid--4 {
    grid-template-columns: 1fr;
  }
}

/* Margin */
.mt-sm {
  margin-top: var(--spacing-sm);
}
.mt-md {
  margin-top: var(--spacing-md);
}
.mt-lg {
  margin-top: var(--spacing-lg);
}
.mt-xl {
  margin-top: var(--spacing-xl);
}
.mt-2xl {
  margin-top: var(--spacing-2xl);
}
.mb-sm {
  margin-bottom: var(--spacing-sm);
}
.mb-md {
  margin-bottom: var(--spacing-md);
}
.mb-lg {
  margin-bottom: var(--spacing-lg);
}
.mb-xl {
  margin-bottom: var(--spacing-xl);
}
.mb-2xl {
  margin-bottom: var(--spacing-2xl);
}

/* Divider */
.divider {
  height: 1px;
  background: var(--color-border-light);
  margin: var(--spacing-2xl) 0;
}

/* Icon sizing */
.icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.icon--sm {
  width: 16px;
  height: 16px;
}
.icon--md {
  width: 24px;
  height: 24px;
}
.icon--lg {
  width: 32px;
  height: 32px;
}

/* 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;
}

/* ========================
 * 8. Scrollbar
 * ======================== */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: var(--color-bg-page);
}
::-webkit-scrollbar-thumb {
  background: var(--color-text-muted);
  border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover {
  background: var(--color-text-secondary);
}

* {
  scrollbar-width: thin;
  scrollbar-color: var(--color-text-muted) var(--color-bg-page);
}

/* ========================
 * 9. Animations
 * ======================== */
@keyframes fade-in-up {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}