/* PhysicsByYaya design system: tokens, top bar, buttons, lab menu.
   Shared by the homepage and every renovated lab. */

:root {
  --bg: #f4f6f9;
  --surface: #ffffff;
  --surface-2: #eef1f5;
  --ink: #0f1b2d;
  --muted: #556173;
  --line: #dde3ea;
  --brand: #0a7477;
  --brand-strong: #075c5f;
  --brand-ink: #ffffff;
  --brand-soft: #e1f2f2;
  --red: #c2412d;
  --amber: #d99311;
  --blue: #2463c9;
  --green: #2a8048;
  --violet: #6a4cc2;
  --good-soft: #e3f4e8;
  --bad-soft: #fbe7e3;
  --sky-top: #d9eafb;
  --sky-bottom: #eef6fd;
  --ground: #e3e8ee;
  --t1: #0a7477;
  --t2: #c2552d;
  --t3: #2463c9;
  --t4: #a8730a;
  --t5: #2a8048;
  --t6: #5b4bc4;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow: 0 1px 2px rgba(15, 27, 45, 0.05), 0 6px 20px rgba(15, 27, 45, 0.06);
  --shadow-lg: 0 20px 50px rgba(15, 27, 45, 0.18);
  --bar-h: 56px;
  --font: Inter, ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}

:root[data-theme="dark"] {
  --bg: #0c121d;
  --surface: #151d2c;
  --surface-2: #1d273a;
  --ink: #e9eef6;
  --muted: #9ba8bb;
  --line: #2a3650;
  --brand: #3dc4c6;
  --brand-strong: #6fd9da;
  --brand-ink: #062a2b;
  --brand-soft: #143538;
  --red: #f0806b;
  --amber: #f2b84b;
  --blue: #7aa7f5;
  --green: #6fca8b;
  --violet: #a996f0;
  --good-soft: #173524;
  --bad-soft: #3d1f1a;
  --sky-top: #131c2e;
  --sky-bottom: #19253a;
  --ground: #222d42;
  --t1: #3dc4c6;
  --t2: #f0926b;
  --t3: #7aa7f5;
  --t4: #f2b84b;
  --t5: #6fca8b;
  --t6: #a996f0;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 6px 20px rgba(0, 0, 0, 0.25);
  --shadow-lg: 0 20px 50px rgba(0, 0, 0, 0.55);
  color-scheme: dark;
}

[data-topic="1"] { --topic: var(--t1); }
[data-topic="2"] { --topic: var(--t2); }
[data-topic="3"] { --topic: var(--t3); }
[data-topic="4"] { --topic: var(--t4); }
[data-topic="5"] { --topic: var(--t5); }
[data-topic="6"] { --topic: var(--t6); }

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-padding-top: calc(var(--bar-h) + 16px);
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 1rem;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
p {
  margin: 0;
}

h1,
h2,
h3 {
  line-height: 1.15;
  letter-spacing: -0.015em;
  text-wrap: balance;
}

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

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

:focus-visible {
  outline: 3px solid var(--brand);
  outline-offset: 2px;
  border-radius: 6px;
}

.kicker {
  color: var(--topic, var(--brand));
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

/* The hidden attribute must win over any display rule on a component. */
[hidden] {
  display: none !important;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

/* ---------- Buttons ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 40px;
  padding: 8px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  font-weight: 700;
  font-size: 0.9rem;
  text-decoration: none;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s, transform 0.1s;
}

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

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

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

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

.btn-ghost {
  background: transparent;
  border-color: transparent;
}

.btn-ghost:hover {
  background: var(--surface-2);
  border-color: transparent;
}

.btn[aria-pressed="true"] {
  background: var(--brand-soft);
  border-color: var(--brand);
  color: var(--brand-strong);
}

.btn svg {
  width: 18px;
  height: 18px;
  flex: none;
}

.btn-icon {
  width: 40px;
  padding: 0;
}

/* ---------- Top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  gap: 16px;
  height: var(--bar-h);
  padding: 0 max(16px, env(safe-area-inset-left)) 0 max(16px, env(safe-area-inset-right));
  background: color-mix(in srgb, var(--surface) 88%, transparent);
  border-bottom: 1px solid var(--line);
  backdrop-filter: saturate(1.4) blur(12px);
  -webkit-backdrop-filter: saturate(1.4) blur(12px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  color: var(--ink);
  font-weight: 800;
  letter-spacing: -0.01em;
  text-decoration: none;
  white-space: nowrap;
}

.brand img {
  width: 28px;
  height: 28px;
  border-radius: 7px;
}

/* The PhysicsByYaya wordmark: bold italic serif, "Yaya" in the logo orange. */
.wordmark {
  font-family: Georgia, "Times New Roman", Times, serif;
  font-style: italic;
  font-weight: 700;
  font-size: 1.3rem;
  letter-spacing: 0.005em;
  line-height: 1;
  color: var(--ink);
}

.wordmark em {
  font-style: italic;
  color: #e8822e;
}

.crumbs {
  display: flex;
  align-items: center;
  gap: 8px;
  min-width: 0;
  color: var(--muted);
  font-size: 0.875rem;
}

.crumbs a {
  color: var(--muted);
  text-decoration: none;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

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

.crumbs strong {
  color: var(--ink);
  white-space: nowrap;
}

.bar-actions {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-left: auto;
}

@media (max-width: 760px) {
  .crumbs,
  .bar-actions .btn-label {
    display: none;
  }

  .wordmark {
    font-size: 1.15rem;
  }

  .bar-actions .btn {
    width: 40px;
    padding: 0;
  }
}

/* ---------- Lab menu dialog ---------- */

.lab-menu {
  width: min(880px, calc(100vw - 24px));
  max-height: min(760px, calc(100dvh - 24px));
  padding: 0;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--surface);
  color: var(--ink);
  box-shadow: var(--shadow-lg);
}

.lab-menu::backdrop {
  background: rgba(8, 14, 24, 0.5);
}

.lab-menu-head {
  position: sticky;
  top: 0;
  display: flex;
  gap: 8px;
  padding: 14px;
  background: var(--surface);
  border-bottom: 1px solid var(--line);
}

.search-input {
  flex: 1;
  min-width: 0;
  min-height: 42px;
  padding: 8px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--bg);
  color: var(--ink);
}

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

.lab-menu-body {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 6px 22px;
  padding: 14px 18px 20px;
}

.lab-menu-group h3 {
  margin: 10px 0 4px;
  color: var(--topic);
  font-size: 0.75rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.lab-menu-group a {
  display: block;
  padding: 7px 10px;
  margin: 0 -10px;
  border-radius: 8px;
  color: var(--ink);
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
}

.lab-menu-group a:hover {
  background: var(--surface-2);
}

.lab-menu-group a[aria-current="page"] {
  background: var(--brand-soft);
  color: var(--brand-strong);
}

.lab-menu-empty {
  grid-column: 1 / -1;
  padding: 20px 0;
  color: var(--muted);
}

@media (prefers-reduced-motion: reduce) {
  * {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}