:root {
  --bg: #f3f7fb;
  --ink: #28323f;
  --muted: #6b7785;
  --primary: #4f86c6;
  --primary-dark: #3a6ca8;
  --accent: #ffb703;
  --card: #ffffff;
  --ok: #2e9e5b;
  --radius: 16px;
  --shadow: 0 6px 20px rgba(40, 60, 90, 0.08);
  /* Surfaces & borders (themeable) */
  --surface: #e9eef5;
  --surface-soft: #f7fafe;
  --surface-qa: #f3f0ff;
  --border: #dce3ec;
  --border-soft: #e6ecf3;
  --track: #e3e9f1;
  --key-idea-bg: #fff8e6;
}

[data-theme="dark"] {
  --bg: #11151c;
  --ink: #e6ebf2;
  --muted: #9aa6b4;
  --primary: #6ea8e0;
  --primary-dark: #5891cc;
  --accent: #ffc233;
  --card: #1b212b;
  --ok: #4cc585;
  --shadow: 0 6px 20px rgba(0, 0, 0, 0.45);
  --surface: #2a323f;
  --surface-soft: #232a35;
  --surface-qa: #2b2740;
  --border: #38414f;
  --border-soft: #2c3542;
  --track: #2a323f;
  --key-idea-bg: #2e2a1a;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Comic Neue", "Trebuchet MS", "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.55;
  transition: background-color .2s ease, color .2s ease;
}

.topbar {
  display: flex; align-items: center; justify-content: space-between;
  gap: 1rem; padding: 0.8rem 1.5rem;
  background: var(--card); box-shadow: var(--shadow); position: sticky; top: 0; z-index: 10;
}
.brand { font-size: 1.4rem; font-weight: 800; color: var(--primary); text-decoration: none; }
.topbar nav { display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; }
.topbar nav a { color: var(--ink); text-decoration: none; font-weight: 600; }
.topbar nav a:hover { color: var(--primary); }
.who { color: var(--muted); font-size: 0.9rem; }
.inline { display: inline; margin: 0; }
.link-btn { background: none; border: none; color: var(--primary); cursor: pointer; font: inherit; font-weight: 600; }

/* Dark-mode toggle */
.theme-toggle {
  display: inline-flex; align-items: center; justify-content: center;
  width: 38px; height: 32px; padding: 0; border: none; cursor: pointer;
  border-radius: 999px; background: var(--surface); color: var(--ink);
  transition: background-color .2s ease;
}
.theme-toggle:hover { filter: brightness(0.97); }
.theme-toggle-icon {
  width: 16px; height: 16px; border-radius: 50%;
  /* Crescent moon: a circle with an offset inset shadow carving it out. */
  box-shadow: inset -4px -2px 0 0 currentColor;
  transition: box-shadow .2s ease, background-color .2s ease;
}
[data-theme="dark"] .theme-toggle-icon {
  /* Sun: a filled dot with a soft ring. */
  box-shadow: 0 0 0 2px currentColor;
  background: currentColor;
}

.card, .topbar, .skill-card, .category-accordion, .stat, .timeline-row {
  transition: background-color .2s ease, box-shadow .2s ease;
}

.container { max-width: 880px; margin: 1.5rem auto; padding: 0 1.2rem; }
.footer { text-align: center; color: var(--muted); padding: 2rem 1rem; }
.footer p { margin: 0.25rem 0; }
.footer-info { font-weight: 700; }

h1 { font-size: 2rem; margin: 0.2rem 0; }
h2 { margin-top: 0; }
.muted { color: var(--muted); }
.small { font-size: 0.86rem; }
.center { text-align: center; }

.card {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 1.4rem 1.6rem; margin: 1rem 0;
}
.card.narrow { max-width: 420px; margin: 3rem auto; }
.card.highlight { border: 3px solid var(--accent); }
.card.pick-header { display: flex; align-items: center; justify-content: center; min-height: 6rem; }
.card.pick-header h2 { margin: 0; }

.btn {
  display: inline-block; padding: 0.65rem 1.2rem; border-radius: 999px;
  background: var(--surface); color: var(--ink); border: none; cursor: pointer;
  font: inherit; font-weight: 700; text-decoration: none; transition: transform .05s ease;
}
.btn:hover { transform: translateY(-1px); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }

.row { display: flex; align-items: center; gap: 0.8rem; flex-wrap: wrap; }
.row.spread { justify-content: space-between; }
.stack { display: flex; flex-direction: column; gap: 0.9rem; }
.stack label { font-weight: 600; display: flex; flex-direction: column; gap: 0.3rem; }
input[type=text], input[type=password], textarea {
  padding: 0.6rem 0.7rem; border: 2px solid var(--border); border-radius: 10px; font: inherit; width: 100%;
  background: var(--card); color: var(--ink);
}
input:focus, textarea:focus { outline: none; border-color: var(--primary); }

.pill { display: inline-block; padding: 0.2rem 0.7rem; border-radius: 999px; color: #fff; font-weight: 700; font-size: 0.85rem; }
.badge { display: inline-block; padding: 0.15rem 0.6rem; border-radius: 8px; background: var(--surface); color: var(--ink); font-size: 0.85rem; font-weight: 700; }
.badge.done { background: #d9f3e3; color: var(--ok); }

.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 1rem; }
.skill-card { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1.1rem; display: flex; flex-direction: column; }
.skill-card h4 { margin: 0 0 0.3rem; }
.skill-card form { margin-top: auto; display: flex; justify-content: center; }
/* Skill picker — collapsible category accordions */
.category-accordion {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  margin: 0.7rem 0; overflow: hidden;
}
.category-accordion > summary {
  list-style: none; cursor: pointer; user-select: none;
  display: flex; align-items: center; gap: 0.7rem;
  padding: 0.8rem 1.1rem; font-weight: 800;
  border-left: 6px solid var(--cat-color, var(--primary));
}
.category-accordion > summary::-webkit-details-marker { display: none; }
.category-accordion > summary::after {
  content: "▸"; color: var(--muted); font-size: 1.1rem; transition: transform .15s ease;
}
.category-accordion[open] > summary::after { transform: rotate(90deg); }
.category-accordion > summary:hover { background: var(--surface-soft); }
.category-accordion .cat-name { flex: 1; color: var(--cat-color, var(--ink)); }
.category-accordion .cat-count { color: var(--muted); font-size: 0.8rem; font-weight: 700; }
.category-accordion .grid { padding: 0.2rem 1.1rem 1.1rem; }

.grid.compact { grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 0.7rem; }
.grid.compact .skill-card { box-shadow: none; border: 1px solid var(--border-soft); padding: 0.8rem 0.9rem; }
.grid.compact .skill-card h4 { font-size: 1rem; }
.btn-sm { padding: 0.4rem 0.9rem; font-size: 0.9rem; }

.flash { padding: 0.7rem 1rem; border-radius: 10px; margin-bottom: 0.6rem; font-weight: 600; }
.flash-success { background: #d9f3e3; color: var(--ok); }
.flash-error { background: #fde2e1; color: #c0392b; }
.flash-info, .flash-warning { background: #fff3cd; color: #8a6d3b; }

/* Full-screen loading block (e.g. while a lesson is being generated) */
.loading-overlay {
  position: fixed; inset: 0; z-index: 1000;
  display: flex; align-items: center; justify-content: center;
  padding: 1.2rem; background: rgba(20, 28, 40, 0.55);
}
.loading-overlay[hidden] { display: none; }
.loading-box {
  background: var(--card); color: var(--ink); text-align: center;
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 1.6rem 2rem; max-width: 320px;
}
.loading-box .loading-text { font-weight: 800; margin: 0.9rem 0 0.2rem; }
.loading-box p { margin: 0.2rem 0; }
.spinner {
  width: 44px; height: 44px; margin: 0 auto; border-radius: 50%;
  border: 5px solid var(--border); border-top-color: var(--primary);
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }
body.is-loading { cursor: progress; }
@media (prefers-reduced-motion: reduce) { .spinner { animation: spin 1.8s linear infinite; } }

/* Lesson */
.lesson-head h1 { margin-top: 0.4rem; }
.progressbar { background: var(--track); border-radius: 999px; height: 12px; overflow: hidden; margin: 0.5rem 0 0.2rem; }
.progressbar-fill { background: var(--accent); height: 100%; transition: width .3s ease; }
.lesson-card { font-size: 1.08rem; }
.lesson-body { font-size: 1.12rem; }


.warm-up { background: var(--surface-qa); }
.warm-up-label, .tip-label, .fun-fact-label {
  display: inline-block; font-size: 0.72rem; font-weight: 800; text-transform: uppercase;
  letter-spacing: 0.04em; color: var(--primary); margin-right: 0.4rem;
}
.warm-up-label { display: block; margin-bottom: 0.3rem; }
.tip { background: var(--key-idea-bg); border-radius: 8px; padding: 0.5rem 0.8rem; margin-top: 0.6rem; font-size: 0.98rem; }
.fun-fact { background: var(--surface-soft); font-size: 1.02rem; }
.recap-list { margin: 0.4rem 0 0; padding-left: 1.2rem; }
.recap-list li { margin: 0.25rem 0; }

.question { background: var(--surface-soft); border-radius: 12px; padding: 0.9rem 1.1rem; }
.q-prompt { font-weight: 700; margin: 0 0 0.7rem; }

/* Tappable button options — quiz answers and the wrap-up confirmations */
.choices { display: flex; flex-direction: column; gap: 0.55rem; }
.choice-btn {
  display: flex; align-items: center; gap: 0.7rem;
  padding: 0.7rem 1rem; border: 2px solid var(--border); border-radius: 12px;
  background: var(--card); color: var(--ink); font-weight: 600; cursor: pointer;
  transition: border-color .1s ease, background .1s ease, transform .05s ease;
}
.choice-btn:hover { border-color: var(--primary); transform: translateY(-1px); }
.choice-btn input { position: absolute; opacity: 0; width: 0; height: 0; }
.choice-marker {
  flex: 0 0 auto; width: 22px; height: 22px; border-radius: 999px;
  border: 2px solid var(--border); background: var(--card);
  display: inline-flex; align-items: center; justify-content: center;
  color: #fff; font-size: 0.85rem; font-weight: 800; transition: all .1s ease;
}
.choice-btn:has(input:checked) { border-color: var(--primary); background: var(--key-idea-bg); }
.choice-btn:has(input:checked) .choice-marker { background: var(--primary); border-color: var(--primary); }
.choice-btn:has(input:checked) .choice-marker::after { content: "✓"; }
.choice-btn:has(input:focus-visible) { outline: 2px solid var(--primary); outline-offset: 2px; }
.choice-correct { border-color: #22c55e !important; background: #f0fdf4 !important; color: #14532d !important; }
.choice-correct .choice-marker { background: #22c55e !important; border-color: #22c55e !important; color: #fff; }
.choice-incorrect { border-color: #ef4444 !important; background: #fef2f2 !important; color: #7f1d1d !important; }
.choice-incorrect .choice-marker { background: #ef4444 !important; border-color: #ef4444 !important; color: #fff; }
.choice-btn:disabled { cursor: default; transform: none; }
.q-feedback { margin-top: 0.6rem; font-size: 0.9rem; color: var(--muted); font-style: italic; }
.q-feedback-retry { color: #ef4444; font-style: normal; font-weight: 700; }

.qa { background: var(--surface-qa); }
.qa-answer { background: var(--card); border-radius: 12px; padding: 0.7rem 1rem; margin-top: 0.8rem; }

/* Q&A chat */
.chat-log { display: flex; flex-direction: column; gap: 0.5rem; margin: 0.8rem 0; }
.chat-log:empty { margin: 0; }
.bubble {
  max-width: 85%; padding: 0.6rem 0.9rem; border-radius: 16px;
  line-height: 1.4; white-space: pre-wrap; overflow-wrap: anywhere;
}
.bubble-user { align-self: flex-end; background: var(--primary); color: #fff; border-bottom-right-radius: 4px; }
.bubble-bot { align-self: flex-start; background: var(--card); color: var(--ink); border-bottom-left-radius: 4px; }
.bubble-thinking { color: var(--muted); font-size: 1.3rem; letter-spacing: 0.1em; padding: 0.3rem 0.9rem; }

.primers { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-bottom: 0.7rem; }
.primer-chip {
  background: var(--card); border: 2px solid var(--border); border-radius: 999px;
  padding: 0.45rem 0.9rem; font: inherit; font-weight: 600; font-size: 0.92rem;
  color: var(--ink); cursor: pointer; text-align: left;
  transition: border-color .1s ease, transform .05s ease;
}
.primer-chip:hover { border-color: var(--primary); transform: translateY(-1px); }
.primer-chip::before { content: "💬 "; }

.chat-input-row { display: flex; gap: 0.6rem; align-items: center; }
.chat-input-row input { flex: 1; }

.task { margin: 1rem 0; }

.stats { display: flex; gap: 1rem; flex-wrap: wrap; }
.stat { background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow); padding: 1rem 1.4rem; flex: 1; min-width: 140px; }
.stat .big { display: block; font-size: 2rem; font-weight: 800; color: var(--primary); }

.timeline { margin-top: 1rem; }
.timeline-row { display: flex; gap: 0.8rem; align-items: flex-start; background: var(--card); border-radius: 12px; box-shadow: var(--shadow); padding: 0.8rem 1rem; margin-bottom: 0.6rem; }
.timeline-body { flex: 1; }
.link { color: var(--primary); font-weight: 700; text-decoration: none; margin-left: 0.5rem; }

/* Celebration page */
.confetti-canvas { position: fixed; top: 0; left: 0; width: 100%; height: 100%; pointer-events: none; z-index: 0; }
.celebrate-card { position: relative; z-index: 1; text-align: center; max-width: 480px; margin: 3rem auto; padding: 2.5rem 2rem; }
.celebrate-emoji { font-size: 4rem; line-height: 1; margin-bottom: 0.5rem; }
.celebrate-skill { font-size: 1.3rem; font-weight: 800; color: var(--primary); margin: 0.2rem 0 1rem; }

/* Completed dashboard card */
.completed-card { border: 2px solid var(--accent); }
.completed-banner { display: flex; justify-content: center; gap: 0.4rem; margin-bottom: 0.6rem; }
.completed-star { font-size: 1.6rem; animation: star-pop 0.4s ease both; }
.completed-star:nth-child(2) { animation-delay: 0.1s; }
.completed-star:nth-child(3) { animation-delay: 0.2s; }
@keyframes star-pop { from { transform: scale(0); opacity: 0; } to { transform: scale(1); opacity: 1; } }
.completed-skill-name { font-size: 1.25rem; font-weight: 800; color: var(--primary); margin: 0.2rem 0 0.4rem; }

/* Review archive (past completed lessons) */
.review-section { margin-top: 1.5rem; border-top: 2px dashed var(--border); }
.review-section h3 { margin: 0.2rem 0 0.4rem; }
.review-tag { display: inline-block; font-weight: 700; font-size: 0.85rem; color: var(--primary);
  background: var(--surface-2, rgba(127, 127, 127, 0.12)); border-radius: 999px;
  padding: 0.1rem 0.6rem; margin-left: 0.4rem; }