/* Reset + base layout shell */

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

* {
  margin: 0;
}

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

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  background-image:
    radial-gradient(60% 50% at 100% 0%, var(--color-accent-soft) 0%, transparent 60%),
    radial-gradient(50% 45% at 0% 100%, var(--color-warm-soft) 0%, transparent 55%);
  background-attachment: fixed;
  transition: background-color var(--duration-normal) var(--ease-out-expo),
    color var(--duration-normal) var(--ease-out-expo);
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  line-height: 1.15;
  font-weight: 600;
  color: var(--color-text);
}

a {
  color: var(--color-accent-strong);
  text-decoration: none;
}

button {
  font: inherit;
  cursor: pointer;
}

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

:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

.skip-link {
  position: absolute;
  left: -999px;
  top: var(--space-2);
  z-index: 100;
  background: var(--color-surface);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
}
.skip-link:focus {
  left: var(--space-2);
}

/* ---------- Header ---------- */

.app-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-5);
  background: oklch(from var(--color-surface) l c h / 0.82);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--color-text);
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--color-accent) 0%, var(--color-accent-strong) 100%);
  color: white;
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: 0.02em;
  box-shadow: var(--shadow-sm);
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}
.brand-text strong {
  font-family: var(--font-display);
  font-size: var(--text-lg);
}
.brand-text small {
  color: var(--color-text-faint);
  font-size: var(--text-xs);
}

.main-nav {
  display: flex;
  gap: var(--space-1);
  margin-left: auto;
}
.main-nav a {
  display: flex;
  flex-direction: column;
  align-items: center;
  line-height: 1.05;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  color: var(--color-text-soft);
  transition: background var(--duration-fast), color var(--duration-fast);
}
.main-nav a small {
  font-size: 0.66rem;
  color: var(--color-text-faint);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.main-nav a:hover {
  background: var(--color-surface-2);
  color: var(--color-text);
}
.main-nav a[aria-current="page"] {
  background: var(--color-accent-soft);
  color: var(--color-accent-strong);
}
.main-nav a[aria-current="page"] small {
  color: var(--color-accent-strong);
}

.theme-toggle {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  color: var(--color-text);
  font-size: 1.3rem;
  transition: transform var(--duration-fast), background var(--duration-fast);
}
.theme-toggle:hover {
  transform: rotate(20deg);
  background: var(--color-surface-2);
}

/* ---------- Main & footer ---------- */

.app-main {
  flex: 1;
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding: var(--space-section) var(--space-5);
}

.app-footer {
  text-align: center;
  padding: var(--space-5);
  color: var(--color-text-faint);
  font-size: var(--text-sm);
  border-top: 1px solid var(--color-border);
}

/* ---------- View transitions ---------- */

.view {
  animation: fade-up var(--duration-normal) var(--ease-out-expo) both;
}

@keyframes fade-up {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ---------- Responsive ---------- */

@media (max-width: 680px) {
  .app-header {
    flex-wrap: wrap;
    padding: var(--space-3) var(--space-4);
  }
  .brand-text small { display: none; }

  /* Top nav cuộn ngang: các mục không co, vuốt ngang được, ẩn thanh cuộn */
  .main-nav {
    order: 3;
    width: 100%;
    margin-left: 0;
    margin-inline: calc(var(--space-4) * -1); /* tràn ra mép để cuộn sát viền */
    padding-inline: var(--space-4);
    justify-content: flex-start;
    flex-wrap: nowrap;
    overflow-x: auto;
    scroll-snap-type: x proximity;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none; /* Firefox */
  }
  .main-nav::-webkit-scrollbar { display: none; } /* WebKit */
  .main-nav a {
    flex: 0 0 auto;
    min-height: 44px;
    justify-content: center;
    scroll-snap-align: start;
  }
  .main-nav a small { font-size: 0.6rem; }
  .theme-toggle { margin-left: auto; }
  .app-main { padding: var(--space-5) var(--space-4); }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}