:root {
  --green-900: #14331f;
  --green-700: #1f6b3a;
  --green-600: #2b8b4c;
  --green-500: #37a15b;
  --green-100: #e7f4ec;
  --amber: #e0a91b;
  --amber-dark: #b9860a;
  --red-600: #d64545;
  --red-100: #fbe9e9;
  --ink: #1d2620;
  --muted: #667a6e;
  --line: #dbe5de;
  --bg: #f4f7f4;
  --card: #ffffff;
  --shadow: 0 2px 8px rgba(20, 51, 31, .08);
  --shadow-lg: 0 12px 40px rgba(20, 51, 31, .16);
  --radius: 14px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.5;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ---------- Top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  background: linear-gradient(120deg, var(--green-900), var(--green-700));
  color: #fff;
  box-shadow: var(--shadow);
}
.topbar-inner {
  max-width: 1100px; margin: 0 auto; padding: 10px 18px;
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
}
.brand { display: flex; align-items: center; gap: 12px; cursor: pointer; user-select: none; }
.brand-mark { font-size: 26px; line-height: 1; }
.brand-txt { display: flex; flex-direction: column; }
.brand-txt strong { font-size: 16px; letter-spacing: .2px; }
.brand-txt small { font-size: 12px; opacity: .82; }
.topbar-actions { display: flex; align-items: center; gap: 14px; }
.topbar-actions[hidden] { display: none; }
.global-progress { display: flex; align-items: center; gap: 8px; min-width: 150px; }
.global-progress-bar { flex: 1; height: 8px; background: rgba(255,255,255,.22); border-radius: 99px; overflow: hidden; }
.global-progress-bar span { display: block; height: 100%; width: 0; background: var(--amber); border-radius: 99px; transition: width .5s ease; }
.global-progress-label { font-size: 12px; font-variant-numeric: tabular-nums; opacity: .95; min-width: 34px; text-align: right; }

/* ---------- Layout ---------- */
.app { flex: 1; max-width: 1100px; width: 100%; margin: 0 auto; padding: 24px 18px 48px; }
.footer { text-align: center; font-size: 12px; color: var(--muted); padding: 18px; border-top: 1px solid var(--line); background: var(--card); }

/* ---------- User chip ---------- */
.user-chip { display: flex; align-items: center; gap: 8px; padding-left: 10px; border-left: 1px solid rgba(255,255,255,.25); }
.user-chip-name { font-size: 13px; font-weight: 600; color: #fff; }

/* ---------- Auth screen ---------- */
.auth-wrap { max-width: 400px; margin: 40px auto; }
.auth-card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 30px 28px; box-shadow: var(--shadow-lg); }
.auth-card h2 { margin: 0 0 6px; text-align: center; }
.auth-card .auth-sub { margin: 0 0 22px; text-align: center; color: var(--muted); font-size: 13.5px; }
.auth-tabs { display: flex; gap: 6px; background: var(--bg); border-radius: 10px; padding: 4px; margin-bottom: 20px; }
.auth-tab { flex: 1; border: none; background: transparent; padding: 9px; border-radius: 8px; font: inherit; font-weight: 600; color: var(--muted); cursor: pointer; }
.auth-tab.active { background: var(--card); color: var(--green-700); box-shadow: var(--shadow); }
.auth-field { display: flex; flex-direction: column; gap: 6px; margin-bottom: 16px; }
.auth-field label { font-size: 13px; font-weight: 600; color: var(--ink); }
.auth-field input {
  font: inherit; padding: 11px 13px; border: 1.5px solid var(--line); border-radius: 9px;
  background: #fff; color: var(--ink);
}
.auth-field input:focus { outline: none; border-color: var(--green-500); }
.auth-error { background: var(--red-100); color: var(--red-600); border-radius: 9px; padding: 10px 13px; font-size: 13.5px; margin-bottom: 16px; }
.auth-submit { width: 100%; margin-top: 4px; }
.auth-hint { margin-top: 16px; text-align: center; font-size: 12.5px; color: var(--muted); }

/* ---------- Buttons ---------- */
.btn {
  font: inherit; font-weight: 600; cursor: pointer; border: 1px solid transparent;
  border-radius: 10px; padding: 11px 18px; background: var(--green-600); color: #fff;
  transition: transform .05s ease, background .15s ease, box-shadow .15s ease;
}
.btn:hover { background: var(--green-700); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn-secondary { background: #fff; color: var(--green-700); border-color: var(--line); }
.btn-secondary:hover { background: var(--green-100); }
.btn-ghost { background: transparent; color: #fff; border-color: rgba(255,255,255,.4); }
.btn-ghost:hover { background: rgba(255,255,255,.14); }
.btn-sm { padding: 7px 12px; font-size: 13px; border-radius: 8px; }
.btn-amber { background: var(--amber); color: #3a2c00; }
.btn-amber:hover { background: var(--amber-dark); color: #fff; }

/* ---------- Hero / intro ---------- */
.hero {
  background: linear-gradient(120deg, var(--green-900), var(--green-600));
  color: #fff; border-radius: var(--radius); padding: 28px 26px; margin-bottom: 24px;
  box-shadow: var(--shadow-lg); position: relative; overflow: hidden;
}
.hero h1 { margin: 0 0 6px; font-size: 26px; }
.hero p { margin: 0; max-width: 640px; opacity: .92; }
.hero .hero-meta { margin-top: 14px; font-size: 13px; opacity: .85; }
.hero-emoji { position: absolute; right: -10px; bottom: -20px; font-size: 130px; opacity: .12; }

.section-title { font-size: 15px; text-transform: uppercase; letter-spacing: .6px; color: var(--muted); margin: 0 0 14px; }

/* ---------- Course menu ---------- */
.course-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 16px; }
.course-card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px; display: flex; align-items: center; gap: 16px; box-shadow: var(--shadow);
  cursor: pointer; transition: transform .1s ease, box-shadow .15s ease, border-color .15s ease;
}
.course-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-lg); border-color: var(--green-500); }
.course-card.completed { border-color: var(--green-500); }
.course-emoji {
  flex: 0 0 auto; width: 60px; height: 60px; border-radius: 16px; display: grid; place-items: center;
  font-size: 32px; background: linear-gradient(135deg, var(--green-100), #d3ecd9);
}
.course-body { flex: 1; min-width: 0; }
.course-body h3 { margin: 0 0 3px; font-size: 18px; }
.course-body p { margin: 0; font-size: 13px; color: var(--muted); }
.course-meta { display: flex; flex-wrap: wrap; gap: 7px; margin: 10px 0 12px; }
.course-progress { display: flex; align-items: center; gap: 9px; }
.course-progress-bar { flex: 1; height: 7px; background: var(--line); border-radius: 99px; overflow: hidden; }
.course-progress-bar span { display: block; height: 100%; background: var(--green-500); border-radius: 99px; transition: width .4s ease; }
.course-progress-label { font-size: 12px; color: var(--muted); font-variant-numeric: tabular-nums; }
.course-arrow { flex: 0 0 auto; font-size: 28px; color: var(--green-500); line-height: 1; }

.crumb-bar { margin-bottom: 14px; }
.loading { text-align: center; color: var(--muted); padding: 40px; font-size: 15px; }

/* ---------- Topic list ---------- */
.topic-grid { display: grid; grid-template-columns: 1fr; gap: 14px; }
.topic-card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px 20px; display: flex; align-items: center; gap: 18px; box-shadow: var(--shadow);
  transition: transform .1s ease, box-shadow .15s ease, border-color .15s ease;
}
.topic-card.clickable { cursor: pointer; }
.topic-card.clickable:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); border-color: var(--green-500); }
.topic-card.locked { opacity: .62; background: #f6f8f6; }
.topic-num {
  flex: 0 0 auto; width: 46px; height: 46px; border-radius: 12px;
  display: grid; place-items: center; font-weight: 700; font-size: 18px;
  background: var(--green-100); color: var(--green-700);
}
.topic-card.completed .topic-num { background: var(--green-600); color: #fff; }
.topic-card.locked .topic-num { background: #e3e8e4; color: #93a29a; }
.topic-body { flex: 1; min-width: 0; }
.topic-body h3 { margin: 0 0 3px; font-size: 17px; }
.topic-body p { margin: 0; font-size: 13.5px; color: var(--muted); }
.topic-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 9px; }
.chip {
  font-size: 11.5px; font-weight: 600; padding: 3px 9px; border-radius: 99px;
  background: var(--green-100); color: var(--green-700);
}
.chip.slides { background: #eef1ff; color: #3b4b9e; }
.chip.pass { background: var(--green-600); color: #fff; }
.chip.fail { background: var(--red-100); color: var(--red-600); }
.topic-status { flex: 0 0 auto; font-size: 22px; }

/* ---------- Slide viewer ---------- */
.viewer-head { display: flex; align-items: center; justify-content: space-between; gap: 14px; margin-bottom: 14px; flex-wrap: wrap; }
.viewer-head h2 { margin: 0; font-size: 20px; }
.crumb { font-size: 13px; color: var(--muted); margin-bottom: 4px; }
.slide-stage {
  background: #0d1712; border-radius: var(--radius); padding: 10px; box-shadow: var(--shadow-lg);
  display: grid; place-items: center; position: relative;
}
.slide-stage img { max-width: 100%; max-height: 72vh; border-radius: 6px; display: block; }
.slide-nav { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-top: 14px; }
.slide-counter { font-size: 14px; color: var(--muted); font-variant-numeric: tabular-nums; }
.slide-progress { height: 6px; background: var(--line); border-radius: 99px; overflow: hidden; margin-top: 12px; }
.slide-progress span { display: block; height: 100%; background: var(--green-500); border-radius: 99px; transition: width .3s ease; }
.viewer-foot { margin-top: 20px; display: flex; justify-content: space-between; align-items: center; gap: 12px; flex-wrap: wrap; }
.hint { font-size: 12.5px; color: var(--muted); }

/* thumbnails strip */
.thumbs { display: flex; gap: 8px; overflow-x: auto; padding: 12px 2px 4px; margin-top: 6px; }
.thumbs img { height: 54px; border-radius: 5px; border: 2px solid transparent; cursor: pointer; opacity: .7; transition: .12s; flex: 0 0 auto; }
.thumbs img:hover { opacity: 1; }
.thumbs img.active { border-color: var(--green-500); opacity: 1; }

/* ---------- Quiz ---------- */
.quiz-wrap { max-width: 760px; margin: 0 auto; }
.quiz-head { text-align: center; margin-bottom: 18px; }
.quiz-head h2 { margin: 0 0 4px; }
.quiz-head p { margin: 0; color: var(--muted); font-size: 14px; }
.quiz-progress { display: flex; align-items: center; gap: 10px; margin: 18px 0 22px; }
.quiz-progress .bar { flex: 1; height: 8px; background: var(--line); border-radius: 99px; overflow: hidden; }
.quiz-progress .bar span { display: block; height: 100%; background: var(--green-500); transition: width .3s ease; }
.quiz-progress .lbl { font-size: 13px; color: var(--muted); font-variant-numeric: tabular-nums; }
.qcard { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow); }
.qtext { font-size: 18px; font-weight: 600; margin: 0 0 18px; }
.options { display: flex; flex-direction: column; gap: 11px; }
.option {
  display: flex; align-items: center; gap: 12px; text-align: left; width: 100%;
  padding: 14px 16px; border: 1.5px solid var(--line); border-radius: 11px;
  background: #fff; font: inherit; cursor: pointer; transition: .12s; color: var(--ink);
}
.option:hover:not(:disabled) { border-color: var(--green-500); background: var(--green-100); }
.option .mark { flex: 0 0 auto; width: 26px; height: 26px; border-radius: 50%; border: 2px solid var(--line); display: grid; place-items: center; font-weight: 700; font-size: 13px; color: var(--muted); }
.option.selected { border-color: var(--green-600); background: var(--green-100); }
.option.selected .mark { border-color: var(--green-600); background: var(--green-600); color: #fff; }
.option.correct { border-color: var(--green-600); background: #e4f6ea; }
.option.correct .mark { background: var(--green-600); border-color: var(--green-600); color: #fff; }
.option.wrong { border-color: var(--red-600); background: var(--red-100); }
.option.wrong .mark { background: var(--red-600); border-color: var(--red-600); color: #fff; }
.option:disabled { cursor: default; }
.explain { margin-top: 16px; padding: 13px 15px; border-radius: 10px; background: #f3f6f3; border-left: 4px solid var(--green-500); font-size: 14px; }
.explain.wrong { background: var(--red-100); border-left-color: var(--red-600); }
.explain strong { display: block; margin-bottom: 3px; }
.quiz-foot { margin-top: 22px; display: flex; justify-content: space-between; align-items: center; gap: 12px; }

/* ---------- Result ---------- */
.result { text-align: center; max-width: 620px; margin: 10px auto; }
.result .badge { font-size: 66px; margin-bottom: 6px; }
.result h2 { margin: 0 0 6px; font-size: 26px; }
.score-ring { --p: 0; width: 150px; height: 150px; margin: 16px auto; border-radius: 50%;
  background: conic-gradient(var(--ring-color) calc(var(--p) * 1%), var(--line) 0);
  display: grid; place-items: center; }
.score-ring .inner { width: 118px; height: 118px; background: var(--card); border-radius: 50%; display: grid; place-items: center; flex-direction: column; }
.score-ring .inner b { font-size: 30px; }
.score-ring .inner small { font-size: 12px; color: var(--muted); }
.result-msg { font-size: 15px; color: var(--muted); margin: 8px auto 22px; }
.result-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.pass .badge, .pass h2 { color: var(--green-700); }
.fail h2 { color: var(--red-600); }

/* review list */
.review { text-align: left; margin-top: 26px; }
.review h3 { font-size: 14px; text-transform: uppercase; letter-spacing: .5px; color: var(--muted); }
.review-item { background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 13px 15px; margin-bottom: 10px; }
.review-item .rq { font-weight: 600; font-size: 14.5px; }
.review-item .ra { font-size: 13.5px; margin-top: 5px; }
.review-item .ra.ok { color: var(--green-700); }
.review-item .ra.no { color: var(--red-600); }

/* ---------- Completion ---------- */
.certificate {
  background: linear-gradient(135deg, #fffdf5, #f0f7f1); border: 2px solid var(--amber);
  border-radius: var(--radius); padding: 34px; text-align: center; box-shadow: var(--shadow-lg);
}
.certificate .seal { font-size: 60px; }
.certificate h2 { margin: 8px 0; color: var(--green-700); }

/* ---------- Misc ---------- */
.notice { background: #fff8e6; border: 1px solid #f0dca0; color: #7a5b00; padding: 12px 15px; border-radius: 10px; font-size: 14px; margin-bottom: 18px; }
.center { text-align: center; }
.mt { margin-top: 18px; }

@media (max-width: 640px) {
  .topbar-inner { flex-wrap: wrap; }
  .global-progress { min-width: 110px; }
  .hero h1 { font-size: 21px; }
  .topic-card { padding: 14px; gap: 12px; }
  .slide-stage img { max-height: 58vh; }
  .qcard { padding: 18px; }
  .qtext { font-size: 16px; }
}