/* css/theme.css
   Design tokens (light, dark) and base element styles.
   Every colour in the site comes from a token defined here. Components use var(--token) only.
   The two dark blocks below must stay identical: one answers the OS preference when the
   student has not chosen, the other answers an explicit choice made with the theme button. */

:root {
  color-scheme: light;

  /* surfaces and text */
  --bg: #f6f3ec;
  --surface: #ffffff;
  --surface-2: #ece8de;
  --text: #1a2230;
  --text-muted: #515b6c;
  --border: #d8d2c4;
  --border-strong: #757d8d;
  --accent: #2f3e5c;
  --on-accent: #ffffff;
  --focus: #1a2230;

  /* the teaching colours */
  --cart: #0b63ad;
  --polar: #a84300;
  --input: #006e53;
  --output: #9d3a8a;
  --seam: #6b7384;
  --t0: #101a30;
  --t1: #6d83a6;
  --ghost-alpha: 0.35;

  /* status */
  --ok: #26702a;
  --warn: #845b00;
  --danger: #b3261e;

  /* theme-dependent non-colour values */
  --shadow: 0 1px 2px rgb(26 34 48 / 0.08), 0 6px 18px rgb(26 34 48 / 0.07);
  --icon-sun: none;
  --icon-moon: block;

  /* typography: system stacks only (no network) */
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-display: "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, "Times New Roman", serif;
  --font-mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;

  /* shape, spacing, layout */
  --radius: 10px;
  --radius-sm: 6px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 1rem;
  --space-4: 1.5rem;
  --space-5: 2.5rem;
  --gutter: 1rem;
  --tap: 2.75rem;
  --header-h: 3.5rem;
  --sidebar-w: 17.5rem;
  --content-max: 72rem;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --bg: #0d121c;
    --surface: #151c2b;
    --surface-2: #1e2739;
    --text: #e9edf5;
    --text-muted: #a6b0c3;
    --border: #2b3650;
    --border-strong: #7480a0;
    --accent: #cfd8ea;
    --on-accent: #0d121c;
    --focus: #e9edf5;
    --cart: #62adf2;
    --polar: #ff9d5c;
    --input: #3fd0a0;
    --output: #e48fd2;
    --seam: #8e99b0;
    --t0: #5c7498;
    --t1: #f3f6fb;
    --ghost-alpha: 0.35;
    --ok: #63d08a;
    --warn: #e3b341;
    --danger: #ff8178;
    --shadow: 0 1px 2px rgb(0 0 0 / 0.5), 0 8px 24px rgb(0 0 0 / 0.45);
    --icon-sun: block;
    --icon-moon: none;
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0d121c;
  --surface: #151c2b;
  --surface-2: #1e2739;
  --text: #e9edf5;
  --text-muted: #a6b0c3;
  --border: #2b3650;
  --border-strong: #7480a0;
  --accent: #cfd8ea;
  --on-accent: #0d121c;
  --focus: #e9edf5;
  --cart: #62adf2;
  --polar: #ff9d5c;
  --input: #3fd0a0;
  --output: #e48fd2;
  --seam: #8e99b0;
  --t0: #5c7498;
  --t1: #f3f6fb;
  --ghost-alpha: 0.35;
  --ok: #63d08a;
  --warn: #e3b341;
  --danger: #ff8178;
  --shadow: 0 1px 2px rgb(0 0 0 / 0.5), 0 8px 24px rgb(0 0 0 / 0.45);
  --icon-sun: block;
  --icon-moon: none;
}

/* ---------- base ---------- */

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

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-padding-top: calc(var(--header-h) + var(--space-3));
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 1.0625rem;
  line-height: 1.55;
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
h4 {
  margin: 0 0 var(--space-2);
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.2;
  text-wrap: balance;
}

h1 { font-size: clamp(1.6rem, 1.25rem + 1.5vw, 2.25rem); }
h2 { font-size: 1.4rem; }
h3 { font-size: 1.15rem; }
h4 { font-size: 1rem; }

p {
  margin: 0 0 var(--space-3);
}

a {
  color: var(--accent);
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.18em;
}

a:hover {
  text-decoration-thickness: 0.14em;
}

code,
kbd,
samp,
pre {
  font-family: var(--font-mono);
  font-size: 0.92em;
}

code {
  padding: 0.1em 0.35em;
  border-radius: 4px;
  background: var(--surface-2);
}

pre {
  margin: 0;
  padding: var(--space-2) var(--space-3);
  overflow-x: auto;
  border-radius: var(--radius-sm);
  background: var(--surface-2);
}

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

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

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

[hidden] {
  display: none !important;
}

::selection {
  background: var(--surface-2);
  color: var(--text);
}

@supports (background: color-mix(in srgb, currentColor 10%, transparent)) {
  ::selection {
    background: color-mix(in srgb, var(--accent) 28%, transparent);
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}