* {
  box-sizing: border-box;
}

:root {
  --color-page: #f3f6f8;
  --color-surface: #ffffff;
  --color-surface-muted: #e5edf0;
  --color-text: #1f2933;
  --color-muted: #52616b;
  --color-border: #a9bcc4;
  --color-brand: #176b73;
  --color-brand-strong: #0d4f56;
  --color-on-brand: #ffffff;
  --color-accent: #c2410c;
  --color-focus: #9a3412;
}

body {
  margin: 0;
  padding: 1.5rem;
  background: var(--color-page);
  color: var(--color-text);
  font-family: Arial, Helvetica, sans-serif;
  font-size: 1rem;
  line-height: 1.5;
}

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

a:focus-visible,
button:focus-visible {
  outline: 3px solid var(--color-focus);
  outline-offset: 3px;
}

.page {
  width: 100%;
  max-width: 64rem;
  margin: 0 auto;
}

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 0 0 1.5rem;
  padding: 0.75rem;
  background: var(--color-surface-muted);
  border: 1px solid var(--color-border);
  border-radius: 0.75rem;
}

nav a {
  flex: 1 1 10rem;
  padding: 0.65rem 0.8rem;
  background: var(--color-surface);
  border: 1px solid var(--color-brand);
  border-radius: 0.5rem;
  font-weight: 700;
  text-align: center;
  text-decoration: none;
}

nav a:hover,
nav a:focus-visible {
  background: var(--color-brand);
  color: var(--color-on-brand);
}

header {
  margin: 0 0 1.5rem;
  padding: 2rem;
  background: var(--color-brand-strong);
  border-radius: 1rem;
  color: var(--color-on-brand);
  text-align: center;
}

header h1,
header p {
  margin: 0;
}

header p {
  margin-top: 0.5rem;
}

.panel {
  margin: 0 0 1.25rem;
  padding: 1.25rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 0.875rem;
}

.panel h2 {
  margin: 0 0 0.75rem;
  color: var(--color-brand-strong);
}

.palette,
.theme-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

.swatch,
.theme-card {
  padding: 1rem;
  background: var(--color-surface);
  border: 2px solid var(--color-border);
  border-radius: 0.75rem;
}

.swatch h3,
.theme-card h3,
.theme-card p {
  margin-top: 0;
}

.swatch-brand {
  background: var(--color-brand);
  border-color: var(--color-brand-strong);
  color: var(--color-on-brand);
}

.swatch-accent {
  border-left: 0.5rem solid var(--color-accent);
}

.code-sample {
  max-width: 100%;
  margin: 0.75rem 0;
  padding: 0.85rem;
  overflow: auto;
  background: var(--color-text);
  border-radius: 0.5rem;
  color: var(--color-surface);
}

code {
  font-family: "Courier New", Courier, monospace;
}

.theme-card {
  --card-surface: var(--color-surface);
  --card-text: var(--color-text);
  --card-border: var(--color-border);
  --card-action: var(--color-brand);
  --card-action-text: var(--color-on-brand);

  background: var(--card-surface);
  border-color: var(--card-border);
  color: var(--card-text);
}

.theme-card-warm {
  --card-surface: #fff7ed;
  --card-text: #431407;
  --card-border: #fb923c;
  --card-action: #c2410c;
  --card-action-text: #ffffff;
}

.theme-card-cool {
  --card-surface: #eff6ff;
  --card-text: #172554;
  --card-border: #60a5fa;
  --card-action: #1d4ed8;
  --card-action-text: #ffffff;
}

.theme-action {
  display: inline-block;
  padding: 0.65rem 0.9rem;
  background: var(--card-action, var(--color-brand));
  border: 2px solid var(--card-action, var(--color-brand));
  border-radius: 0.5rem;
  color: var(--card-action-text, var(--color-on-brand));
  font: inherit;
  font-weight: 700;
  text-decoration: none;
}

.theme-action:hover,
.theme-action:focus-visible {
  background: var(--card-surface, var(--color-surface));
  color: var(--card-action, var(--color-brand));
}

.fallback-demo {
  padding: 1rem;
  background: var(--demo-surface, #fef3c7);
  border-left: 0.5rem solid var(--demo-accent, #b45309);
  color: var(--demo-text, #451a03);
}

@media (min-width: 44rem) {
  .palette,
  .theme-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}


/* 04 — HTML → CSS data channel */
.skill-list {
  display: grid;
  gap: 1rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.skill {
  display: grid;
  gap: 0.35rem;
}

.skill__label {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  font-weight: 700;
}

.skill__track {
  position: relative;
  height: 0.65rem;
  border-radius: 999px;
  background: var(--color-surface-muted);
  overflow: hidden;
}

.skill__fill {
  display: block;
  height: 100%;
  width: 0;
  border-radius: inherit;
  background: var(--color-brand);
  animation: skill-fill 1.4s ease forwards;
}

@keyframes skill-fill {
  from { width: 0; }
  to { width: var(--progress); }
}

@media (prefers-reduced-motion: reduce) {
  .skill__fill {
    animation: none;
    width: var(--progress);
  }
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-page: #0f171a;
    --color-surface: #1a262b;
    --color-surface-muted: #243238;
    --color-text: #e8eef1;
    --color-muted: #a8b6be;
    --color-border: #3d5058;
    --color-brand: #5ec4c8;
    --color-brand-strong: #3aa0a4;
    --color-on-brand: #0f171a;
    --color-accent: #fb923c;
    --color-focus: #fdba74;
  }
}

.scheme-card .scheme-hint {
  color: var(--color-muted);
  font-size: 0.95rem;
}