/* ---------- Theme ---------- */
:root {
  --bg: #f6f7f9;
  --surface: #ffffff;
  --text: #1c2430;
  --muted: #5d6878;
  --border: #dfe3ea;
  --accent: #2f7d4f;
  --accent-soft: #e4f3ea;
  --blocks-bg: #eef1f5;
  --tip: #e8f1fd;
  --tip-border: #3f71b5;
  --warn: #fdf1e3;
  --warn-border: #d0792d;
  --bad: #b3261e;
  --bad-soft: #fbe9e7;
  --mid: #8a5a00;
  --shadow: 0 1px 3px rgba(20, 30, 50, 0.08);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #12161c;
    --surface: #1b212a;
    --text: #e6eaf0;
    --muted: #9aa5b5;
    --border: #2d3644;
    --accent: #6fcf97;
    --accent-soft: #1f3329;
    --blocks-bg: #252d39;
    --tip: #1a2a40;
    --tip-border: #6c9be0;
    --warn: #3a2a18;
    --warn-border: #e09a55;
    --bad: #ff8a80;
    --bad-soft: #3d1f1d;
    --mid: #f0b860;
    --shadow: none;
  }
}
:root[data-theme="dark"] {
  --bg: #12161c;
  --surface: #1b212a;
  --text: #e6eaf0;
  --muted: #9aa5b5;
  --border: #2d3644;
  --accent: #6fcf97;
  --accent-soft: #1f3329;
  --blocks-bg: #252d39;
  --tip: #1a2a40;
  --tip-border: #6c9be0;
  --warn: #3a2a18;
  --warn-border: #e09a55;
  --bad: #ff8a80;
  --bad-soft: #3d1f1d;
  --mid: #f0b860;
  --shadow: none;
}

/* ---------- Base ---------- */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 17px;
  line-height: 1.65;
}
a { color: var(--accent); }
h1, h2, h3 { line-height: 1.25; }
h1 { font-size: 2rem; margin: 0 0 0.4em; }
h2 { font-size: 1.4rem; margin: 2.2em 0 0.6em; padding-top: 0.4em; border-top: 1px solid var(--border); }
h3 { font-size: 1.1rem; margin: 1.6em 0 0.4em; }
code {
  background: var(--blocks-bg);
  padding: 0.1em 0.4em;
  border-radius: 4px;
  font-size: 0.9em;
}
.muted { color: var(--muted); }
.lead { font-size: 1.1rem; color: var(--muted); margin-top: 0; }

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.site-header .inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 10px 16px;
  display: flex;
  align-items: center;
  gap: 8px 20px;
  flex-wrap: wrap;
}
.brand {
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
  margin-right: auto;
}
.brand span { color: var(--accent); }
.site-nav { display: flex; gap: 4px; flex-wrap: wrap; }
.site-nav a {
  color: var(--muted);
  text-decoration: none;
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 0.95rem;
}
.site-nav a:hover { background: var(--blocks-bg); }
.site-nav a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.theme-toggle {
  border: 1px solid var(--border);
  background: transparent;
  color: var(--text);
  border-radius: 6px;
  padding: 5px 10px;
  cursor: pointer;
  font-size: 0.9rem;
}

/* ---------- Layout ---------- */
.page {
  max-width: 1100px;
  margin: 0 auto;
  padding: 28px 16px 60px;
}
.page.narrow { max-width: 860px; }
.with-sidebar {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  gap: 36px;
}
.sidebar { position: sticky; top: 76px; align-self: start; }
.sidebar h4 {
  margin: 0 0 8px;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}
.sidebar ol { list-style: none; margin: 0; padding: 0; counter-reset: lesson; }
.sidebar li { counter-increment: lesson; }
.sidebar a {
  display: block;
  padding: 7px 10px;
  border-radius: 6px;
  color: var(--text);
  text-decoration: none;
  font-size: 0.95rem;
}
.sidebar a::before { content: counter(lesson) ". "; color: var(--muted); }
.sidebar a:hover { background: var(--blocks-bg); }
.sidebar a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.content { min-width: 0; }

@media (max-width: 800px) {
  .with-sidebar { display: block; }
  .sidebar { position: static; margin-bottom: 24px; }
  .sidebar ol { display: flex; gap: 6px; flex-wrap: wrap; }
  .sidebar a { border: 1px solid var(--border); background: var(--surface); }
  h1 { font-size: 1.6rem; }
}

/* ---------- Cards ---------- */
.hero { padding: 20px 0 8px; }
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  margin: 16px 0 8px;
}
.card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 18px;
  box-shadow: var(--shadow);
  color: var(--text);
  text-decoration: none;
}
a.card:hover { border-color: var(--accent); }
.card h3 { margin: 0 0 6px; }
.card p { margin: 0; color: var(--muted); font-size: 0.95rem; }
.card .tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent);
  background: var(--accent-soft);
  border-radius: 999px;
  padding: 2px 10px;
  margin-bottom: 8px;
}
.card .actions { margin-top: 12px; display: flex; gap: 8px; flex-wrap: wrap; }
.btn {
  display: inline-block;
  background: var(--accent);
  color: var(--surface);
  text-decoration: none;
  border-radius: 6px;
  padding: 6px 14px;
  font-size: 0.9rem;
  font-weight: 600;
}
.empty {
  border: 1px dashed var(--border);
  border-radius: 10px;
  padding: 28px;
  text-align: center;
  color: var(--muted);
}

/* ---------- Lesson pieces ---------- */
.note, .warn {
  border-left: 4px solid var(--tip-border);
  background: var(--tip);
  padding: 12px 16px;
  border-radius: 0 8px 8px 0;
  margin: 18px 0;
}
.warn { border-left-color: var(--warn-border); background: var(--warn); }
.note > :first-child, .warn > :first-child { margin-top: 0; }
.note > :last-child, .warn > :last-child { margin-bottom: 0; }

.table-wrap { overflow-x: auto; margin: 16px 0; }
table { border-collapse: collapse; width: 100%; font-size: 0.95rem; }
th, td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; vertical-align: top; }
th { background: var(--blocks-bg); }

details {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 14px;
  margin: 10px 0;
}
details summary { cursor: pointer; font-weight: 600; }
details[open] summary { margin-bottom: 8px; }

.pager {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 48px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}
.pager a { text-decoration: none; font-weight: 600; }

.site-footer {
  text-align: center;
  color: var(--muted);
  font-size: 0.85rem;
  padding: 24px 16px;
  border-top: 1px solid var(--border);
}

/* ---------- App Inventor style blocks ---------- */
.blocks {
  background: var(--blocks-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 16px;
  margin: 16px 0;
  overflow-x: auto;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 14px;
}
.blocks figcaption, .blocks-caption { font-size: 0.85rem; color: var(--muted); margin: -8px 0 16px; }
.blk {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 9px;
  border-radius: 6px;
  color: #fff;
  font-family: "Segoe UI", system-ui, sans-serif;
  font-size: 14px;
  line-height: 1.4;
  white-space: nowrap;
  box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.18);
}
.blk.var   { background: #d05f2d; } /* Variables */
.blk.ctrl  { background: #b18e35; } /* Control   */
.blk.logic { background: #5f9a34; } /* Logic     */
.blk.math  { background: #3f71b5; } /* Math      */
.blk.text  { background: #b32d5e; } /* Text      */
.blk.evt   { background: #a8842c; } /* Component events */
.blk.set   { background: #266643; } /* Component setters */
.blk.get   { background: #439970; } /* Component getters */
.blk .field {
  background: rgba(255, 255, 255, 0.28);
  border-radius: 4px;
  padding: 0 6px;
}
.blk.c { flex-direction: column; align-items: stretch; gap: 5px; }
.blk.c > .row { display: flex; align-items: center; gap: 6px; }
.blk.c > .arm { display: flex; align-items: stretch; gap: 6px; }
.blk.c > .arm > .kw { min-width: 30px; padding-top: 5px; }
.stack {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 4px;
  background: var(--blocks-bg);
  border-radius: 6px 0 0 6px;
  padding: 6px 12px 6px 6px;
  margin-right: -9px;
  min-height: 34px;
}

/* ---------- Student session ---------- */
[hidden] { display: none !important; }
.gated main.content:not(.lock-notice) { display: none; }
.small { font-size: 0.85rem; }
.nowrap { white-space: nowrap; }
.user-box { display: flex; align-items: center; gap: 10px; font-size: 0.9rem; color: var(--muted); }
.link-button {
  border: 0;
  background: none;
  padding: 0;
  color: var(--accent);
  font: inherit;
  text-decoration: underline;
  cursor: pointer;
}
.page-message { max-width: 1068px; margin: 16px auto 0; }
@media (max-width: 1100px) { .page-message { margin-left: 16px; margin-right: 16px; } }
.lock-notice { padding: 40px 0; }

/* Score bands: good (80+), mid (60–79), low (below 60) */
.status { float: right; font-size: 0.75rem; font-weight: 600; color: var(--muted); }
.status.good, .card .tag.good { color: var(--accent); }
.status.mid { color: var(--mid); }
.status.low { color: var(--bad); }
.card .tag.mid { color: var(--mid); background: var(--warn); }
.card .tag.low { color: var(--bad); background: var(--bad-soft); }
.card .tag.todo, .card .tag.locked { color: var(--muted); background: var(--blocks-bg); }
.card.locked { opacity: 0.6; }
@media (max-width: 800px) { .status { float: none; margin-left: 6px; } }

/* ---------- Quiz ---------- */
.quiz .question {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 16px;
  margin: 14px 0;
  min-width: 0;
}
.quiz legend { font-weight: 600; padding: 0 6px; }
.quiz .option { display: flex; align-items: baseline; gap: 10px; padding: 6px 4px; border-radius: 6px; cursor: pointer; }
.quiz .option:hover { background: var(--blocks-bg); }
.quiz .option.is-answer { font-weight: 600; color: var(--accent); }
.quiz .question.correct { border-left: 4px solid var(--accent); }
.quiz .question.wrong { border-left: 4px solid var(--bad); }
.quiz .explain { margin: 8px 0 0; font-size: 0.95rem; color: var(--muted); }
.quiz-actions { display: flex; gap: 10px; margin-top: 16px; }
.quiz-result { border-radius: 8px; scroll-margin-top: 80px; }
.quiz-result.good, .quiz-result.mid, .quiz-result.low, .quiz-result.warn {
  padding: 14px 16px;
  margin: 16px 0;
  border-left: 4px solid var(--accent);
  background: var(--accent-soft);
}
.quiz-result.mid, .quiz-result.warn { border-left-color: var(--warn-border); background: var(--warn); }
.quiz-result.low { border-left-color: var(--bad); background: var(--bad-soft); }
.quiz-result strong { font-size: 1.15rem; }
.quiz-result p { margin: 4px 0 0; }
#quiz { scroll-margin-top: 70px; }

button.btn { border: 0; cursor: pointer; font-family: inherit; }
button.btn:disabled { opacity: 0.6; cursor: default; }
.btn.secondary { background: transparent; color: var(--accent); box-shadow: inset 0 0 0 1px var(--accent); }

/* ---------- Forms (login, dashboard) ---------- */
.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px;
  margin: 16px 0;
  box-shadow: var(--shadow);
}
h2.plain { border-top: 0; margin-top: 0; padding-top: 0; }
.form { display: flex; flex-direction: column; align-items: flex-start; gap: 8px; max-width: 460px; }
.form label { font-weight: 600; font-size: 0.95rem; margin-top: 6px; }
.form input, .form select, .form textarea {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text);
  font: inherit;
}
.form-error { color: var(--bad); font-weight: 600; margin: 4px 0; }
.name-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 8px; margin: 12px 0 16px; }
.name-list.busy { opacity: 0.5; pointer-events: none; }
.name-button {
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font: inherit;
  text-align: left;
  cursor: pointer;
}
.name-button:hover { border-color: var(--accent); }

/* ---------- Teacher dashboard ---------- */
.dash-bar { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; margin-bottom: 12px; }
.tabs { display: flex; gap: 6px; flex-wrap: wrap; margin: 12px 0; }
.tabs button {
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  border-radius: 6px;
  padding: 7px 14px;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
}
.tabs button.active { background: var(--accent); border-color: var(--accent); color: var(--surface); }
.small-tabs button { font-size: 0.9rem; font-weight: 400; padding: 5px 12px; }
.small-tabs button.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
table.dash td { vertical-align: middle; }
table.dash tr.total td { background: var(--blocks-bg); font-weight: 600; }
.pill {
  display: inline-block;
  min-width: 3.2em;
  text-align: center;
  border-radius: 999px;
  padding: 1px 10px;
  font-size: 0.85rem;
  font-weight: 700;
}
.pill.good { color: var(--accent); background: var(--accent-soft); }
.pill.mid { color: var(--mid); background: var(--warn); }
.pill.low { color: var(--bad); background: var(--bad-soft); }
.pill.todo { color: var(--muted); background: var(--blocks-bg); font-weight: 400; }
.bar { display: inline-block; width: 90px; height: 8px; border-radius: 4px; background: var(--blocks-bg); vertical-align: middle; overflow: hidden; }
.bar .fill { display: block; height: 100%; }
.bar .fill.good { background: var(--accent); }
.bar .fill.mid { background: var(--warn-border); }
.bar .fill.low { background: var(--bad); }
.plain-list { list-style: none; margin: 0; padding: 0; }
.plain-list li { padding: 4px 0; }
.narrow-col { max-width: 640px; }
.row-actions { white-space: nowrap; }
.row-actions .link-button + .link-button { margin-left: 14px; }

/* ---------- Home: the lesson to do next ---------- */
.next-lesson { border-left: 4px solid var(--accent); }
.next-lesson .eyebrow {
  display: block;
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  margin-bottom: 4px;
}
.next-lesson p { margin: 6px 0 14px; color: var(--muted); }
.btn.danger { background: var(--bad); margin-bottom: 20px; }