:root {
  --bg: #f7f7f5;
  --surface: #ffffff;
  --surface-2: #f0efeb;
  --text: #1d1d1b;
  --muted: #66655f;
  --border: #dcdad3;
  --accent: #2f5bd3;
  --accent-text: #ffffff;
  --ok: #1f7a4d;
  --ok-bg: #e3f3ea;
  --err: #b42318;
  --err-bg: #fbe7e5;
  --warn-bg: #fff4d6;
  --warn: #8a5a00;
  --code-bg: #f3f2ee;
  --tok-comment: #4f7a3a;
  --tok-string: #a3412a;
  --tok-keyword: #2f5bd3;
  --radius: 8px;
  --mono: ui-monospace, "Cascadia Code", Consolas, monospace;
  color-scheme: light;
}
/* Dark palette: used when the visitor picks dark, or picks nothing and their system is dark. */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #151514;
    --surface: #1f1f1d;
    --surface-2: #2a2a27;
    --text: #ecebe6;
    --muted: #a3a29b;
    --border: #3a3a36;
    --accent: #7c9cff;
    --accent-text: #0f1220;
    --ok: #6fd3a0;
    --ok-bg: #173527;
    --err: #ff8a80;
    --err-bg: #3d1d1a;
    --warn-bg: #3a3218;
    --warn: #f2c14e;
    --code-bg: #11110f;
    --tok-comment: #8fb87a;
    --tok-string: #e6a07a;
    --tok-keyword: #9db4ff;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #151514;
  --surface: #1f1f1d;
  --surface-2: #2a2a27;
  --text: #ecebe6;
  --muted: #a3a29b;
  --border: #3a3a36;
  --accent: #7c9cff;
  --accent-text: #0f1220;
  --ok: #6fd3a0;
  --ok-bg: #173527;
  --err: #ff8a80;
  --err-bg: #3d1d1a;
  --warn-bg: #3a3218;
  --warn: #f2c14e;
  --code-bg: #11110f;
  --tok-comment: #8fb87a;
  --tok-string: #e6a07a;
  --tok-keyword: #9db4ff;
  color-scheme: dark;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
a { color: var(--accent); }
code, pre { font-family: var(--mono); font-size: 0.9em; }
pre { background: var(--surface-2); padding: 12px; border-radius: var(--radius); overflow-x: auto; }
h1 { font-size: 1.8rem; margin: 0 0 4px; }
h2 { font-size: 1.2rem; margin: 0 0 12px; }
.lead { color: var(--muted); margin: 0 0 24px; }

/* Header */
.site-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.site-header .inner { max-width: 1100px; margin: 0 auto; padding: 12px 16px; display: flex; flex-wrap: wrap; gap: 8px 20px; align-items: center; }
.brand { font-weight: 700; text-decoration: none; color: var(--text); display: inline-flex; align-items: center; gap: 8px; }
.brand img { image-rendering: pixelated; }
.site-nav { display: flex; flex-wrap: wrap; gap: 4px 14px; }
.site-nav a { text-decoration: none; color: var(--muted); font-size: 0.95rem; }
.site-nav a:hover, .site-nav a[aria-current="page"] { color: var(--text); }
.theme-toggle {
  margin-left: auto; padding: 4px 12px; font-size: 0.85rem; font-weight: 600;
  background: var(--surface-2); color: var(--text); border: 1px solid var(--border); border-radius: 999px;
}
.theme-toggle:hover { border-color: var(--accent); }

main { max-width: 1100px; margin: 0 auto; padding: 28px 16px 64px; }
.site-footer { text-align: center; color: var(--muted); font-size: 0.85rem; padding: 24px 16px; }

/* Layout */
.grid { display: grid; gap: 16px; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; }
.card h2 { margin-bottom: 8px; }
.card p { margin: 0 0 10px; color: var(--muted); }
a.card { display: block; text-decoration: none; color: inherit; }
a.card:hover { border-color: var(--accent); }
.stack > * + * { margin-top: 12px; }
.row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }

/* Forms */
label { display: block; font-weight: 600; font-size: 0.92rem; margin-bottom: 4px; }
.field { margin-bottom: 14px; }
.field-inline label { display: inline; font-weight: 400; margin-right: 12px; }
input[type="text"], input[type="email"], input[type="password"], input[type="number"], input[type="date"],
input[type="tel"], input[type="url"], input[type="search"], select, textarea {
  width: 100%; padding: 8px 10px; font: inherit; color: var(--text);
  background: var(--surface); border: 1px solid var(--border); border-radius: 6px;
}
input:focus, select:focus, textarea:focus, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
input[aria-invalid="true"], select[aria-invalid="true"], textarea[aria-invalid="true"] { border-color: var(--err); }
.error-text { color: var(--err); font-size: 0.85rem; margin-top: 4px; min-height: 1em; }
.hint { color: var(--muted); font-size: 0.85rem; }

button, .btn {
  display: inline-block; font: inherit; font-weight: 600; cursor: pointer;
  padding: 8px 16px; border-radius: 6px; border: 1px solid var(--accent);
  background: var(--accent); color: var(--accent-text); text-decoration: none;
}
button.secondary, .btn.secondary { background: transparent; color: var(--accent); }
button.danger { background: var(--err); border-color: var(--err); color: #fff; }
button:disabled { opacity: 0.45; cursor: not-allowed; }
button.small { padding: 3px 10px; font-size: 0.85rem; }

/* Feedback */
.alert { padding: 10px 14px; border-radius: 6px; margin: 12px 0; }
.alert.success { background: var(--ok-bg); color: var(--ok); }
.alert.error { background: var(--err-bg); color: var(--err); }
.alert.info { background: var(--warn-bg); }
.hidden { display: none !important; }
.output { font-family: var(--mono); font-size: 0.85rem; background: var(--surface-2); padding: 10px; border-radius: 6px; white-space: pre-wrap; min-height: 2.5em; }

/* Tables */
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; background: var(--surface); }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); white-space: nowrap; }
th { background: var(--surface-2); font-size: 0.9rem; }
th button.sort { all: unset; cursor: pointer; font-weight: 700; }
th[aria-sort="ascending"] button.sort::after { content: " ▲"; }
th[aria-sort="descending"] button.sort::after { content: " ▼"; }
.pager { display: flex; gap: 6px; align-items: center; margin-top: 10px; flex-wrap: wrap; }

/* Widgets */
.spinner { width: 28px; height: 28px; border: 3px solid var(--border); border-top-color: var(--accent); border-radius: 50%; animation: spin 0.8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.progress { height: 14px; background: var(--surface-2); border-radius: 7px; overflow: hidden; }
.progress > div { height: 100%; width: 0; background: var(--accent); transition: width 0.1s linear; }

.drop-zone { min-height: 110px; border: 2px dashed var(--border); border-radius: var(--radius); padding: 10px; display: flex; flex-wrap: wrap; gap: 8px; align-content: flex-start; }
.drop-zone.over { border-color: var(--accent); background: var(--surface-2); }
.draggable { padding: 6px 12px; background: var(--surface-2); border: 1px solid var(--border); border-radius: 6px; cursor: grab; user-select: none; }

.hover-menu { position: relative; display: inline-block; }
.hover-menu .menu { display: none; position: absolute; top: 100%; left: 0; z-index: 5; background: var(--surface); border: 1px solid var(--border); border-radius: 6px; min-width: 160px; padding: 4px 0; }
.hover-menu:hover .menu, .hover-menu:focus-within .menu { display: block; }
.menu a, .menu button { display: block; width: 100%; text-align: left; padding: 6px 12px; background: none; border: 0; color: var(--text); font-weight: 400; text-decoration: none; border-radius: 0; }
.menu a:hover, .menu button:hover { background: var(--surface-2); }

.context-target { padding: 24px; text-align: center; border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface-2); user-select: none; }
#context-menu { position: fixed; z-index: 20; background: var(--surface); border: 1px solid var(--border); border-radius: 6px; padding: 4px 0; min-width: 150px; }

dialog { border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface); color: var(--text); max-width: min(440px, calc(100vw - 32px)); }
dialog::backdrop { background: rgb(0 0 0 / 0.45); }

.badge { display: inline-block; font-size: 0.75rem; padding: 1px 8px; border-radius: 999px; background: var(--surface-2); color: var(--muted); }

/* Difficulty tags: green = easy, amber = medium, red = hard; grey = type of practice */
.tag { display: inline-block; font-size: 0.75rem; font-weight: 700; padding: 2px 10px; border-radius: 999px; white-space: nowrap; }
.tag.easy { background: var(--ok-bg); color: var(--ok); }
.tag.medium { background: var(--warn-bg); color: var(--warn); }
.tag.hard { background: var(--err-bg); color: var(--err); }
.tag.kind { background: var(--surface-2); color: var(--muted); }
.tag.nightmare { background: #1d0f2b; color: #e2c8ff; }
.tags { display: inline-flex; gap: 6px; flex-wrap: wrap; }

/* Home page */
.area-list { display: flex; flex-direction: column; gap: 16px; }
.area-head { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 8px; margin-bottom: 6px; }
.area-head h2 { margin: 0; }
.area-cols { display: grid; gap: 4px 24px; grid-template-columns: 1fr; }
@media (min-width: 760px) { .area-cols { grid-template-columns: 1fr 1fr; } }
.area-cols h3 { font-size: 0.95rem; margin: 10px 0 4px; }
.area-cols ul, .area-cols ol { margin: 0; padding-left: 20px; }
.area-cols li { margin: 2px 0; }
.legend { display: flex; flex-wrap: wrap; gap: 8px 18px; align-items: center; margin: 0 0 20px; color: var(--muted); font-size: 0.9rem; }

/* Exercises */
.exercises { display: flex; flex-direction: column; gap: 16px; }
.exercises-intro { margin: 36px 0 12px; }
.exercise-head { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 8px; margin-bottom: 8px; }
.exercise-head h2, .exercise-head h3 { margin: 0; }
.expected { border-left: 3px solid var(--accent); background: var(--surface-2); padding: 8px 12px; border-radius: 0 6px 6px 0; margin: 12px 0; }
.expected p { margin: 0; color: var(--text); }
.expected ul { margin: 4px 0 0; padding-left: 20px; }
details.solution { margin-top: 10px; }
details.solution > summary {
  display: inline-block; cursor: pointer; list-style: none; font-weight: 600; font-size: 0.9rem;
  padding: 5px 14px; border-radius: 6px; border: 1px solid var(--accent); color: var(--accent);
}
details.solution > summary::-webkit-details-marker { display: none; }
details.solution > summary::before { content: "▸ "; }
details.solution[open] > summary::before { content: "▾ "; }
details.solution[open] > summary { background: var(--accent); color: var(--accent-text); }
.code-block { position: relative; margin-top: 10px; }
.code-block pre { background: var(--code-bg); border: 1px solid var(--border); margin: 0; padding: 14px; line-height: 1.5; font-size: 0.85rem; }
.code-block .copy { position: absolute; top: 8px; right: 8px; font-size: 0.75rem; padding: 2px 10px; }
.tok-c { color: var(--tok-comment); font-style: italic; }
.tok-s { color: var(--tok-string); }
.tok-k { color: var(--tok-keyword); font-weight: 600; }

/* Shop */
.product img { width: 100%; aspect-ratio: 4 / 3; object-fit: cover; border-radius: 6px; background: var(--surface-2); }
.price { font-weight: 700; font-size: 1.1rem; }
.cart-line { display: flex; justify-content: space-between; gap: 10px; padding: 8px 0; border-bottom: 1px solid var(--border); flex-wrap: wrap; }
.cart-line input { width: 70px; }