:root {
  --bg: #0a1220;
  --bg-soft: #0f1b31;
  --card: #111f38;
  --line: #274267;
  --text: #e8f0fb;
  --muted: #afbdd6;
  --ok: #3ad0ad;
  --focus: #76c2ff;
  --warn: #ffd166;
  --danger: #ff7b88;
}

body.light {
  --bg: #f2f7ff;
  --bg-soft: #ffffff;
  --card: #ffffff;
  --line: #cce0fb;
  --text: #122033;
  --muted: #425a79;
  --ok: #1f9d79;
  --focus: #0f68b8;
  --warn: #8c6100;
  --danger: #b73750;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  color: var(--text);
  line-height: 1.68;
  background:
    radial-gradient(circle at 82% -10%, #1f3b66 0%, transparent 35%),
    radial-gradient(circle at 0% 20%, #173356 0%, transparent 28%),
    var(--bg);
}

body.light {
  background:
    radial-gradient(circle at 90% -20%, #ddebff 0%, transparent 35%),
    radial-gradient(circle at 0% 15%, #e8f2ff 0%, transparent 28%),
    var(--bg);
}

.wrap {
  max-width: 1040px;
  margin: 0 auto;
  padding: 16px 14px 84px;
}

.hero,
.toc,
.sec {
  border: 1px solid var(--line);
  background: var(--card);
  border-radius: 14px;
}

.hero {
  padding: 16px;
  margin-bottom: 12px;
  background: linear-gradient(135deg, #17365e, #102643 70%);
}

body.light .hero {
  background: linear-gradient(135deg, #dff0ff, #f7fbff 75%);
}

.hero-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
}

.tag {
  margin: 0;
  display: inline-block;
  border: 1px solid #38659b;
  background: #1b3a64;
  color: #d8ebff;
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
}

body.light .tag {
  border-color: #9dc3ee;
  background: #edf5ff;
  color: #245180;
}

.theme-toggle {
  border: 1px solid #4478b5;
  background: #1d406d;
  color: #e8f4ff;
  border-radius: 999px;
  padding: 6px 12px;
  font-weight: 700;
  font-size: 0.8rem;
  cursor: pointer;
}

body.light .theme-toggle {
  border-color: #9ec4ee;
  background: #fff;
  color: #234a77;
}

h1,
h2,
h3 {
  margin: 0 0 10px;
  line-height: 1.3;
}

h1 {
  margin-top: 8px;
  font-size: clamp(1.2rem, 2.8vw, 1.7rem);
}

h2 {
  font-size: clamp(1.04rem, 2.2vw, 1.28rem);
}

h3 {
  font-size: clamp(0.96rem, 1.9vw, 1.06rem);
}

p {
  margin: 0 0 10px;
  color: var(--muted);
}

.hero p {
  color: #d6e5fb;
}

body.light .hero p {
  color: #345374;
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  margin-top: 10px;
}

.chip {
  border: 1px solid #38659b;
  background: #1b3a64;
  color: #d8ebff;
  padding: 4px 9px;
  border-radius: 999px;
  font-size: 0.75rem;
}

body.light .chip {
  border-color: #a8c9ee;
  background: #edf5ff;
  color: #2c5f92;
}

.hero-actions {
  display: flex;
  gap: 8px;
  margin-top: 12px;
  flex-wrap: wrap;
}

.btn {
  border: 1px solid #2b9a80;
  background: #1e8c74;
  color: #f1fffb;
  border-radius: 999px;
  padding: 7px 12px;
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
  font-size: 0.84rem;
}

.btn-ghost {
  border-color: #4c7cb3;
  background: #1f3f69;
  color: #deefff;
}

body.light .btn {
  border-color: #3f8f7b;
}

body.light .btn-ghost {
  border-color: #a2c3e8;
  background: #f1f7ff;
  color: #29547f;
}

.tip-box {
  min-height: 1.2rem;
  margin-top: 10px;
  color: #d3ebff;
  font-weight: 600;
}

body.light .tip-box {
  color: #2f5c8f;
}

.toc {
  padding: 12px;
  margin-bottom: 12px;
}

.toc ol {
  margin: 6px 0 0;
  padding-left: 20px;
}

.toc a {
  color: #b8d9ff;
  text-decoration: none;
}

body.light .toc a {
  color: #1f609f;
}

.toc a:hover {
  text-decoration: underline;
}

.sec {
  padding: 14px;
  margin-bottom: 12px;
}

ul,
ol {
  margin: 6px 0 10px;
  padding-left: 20px;
}

li {
  margin-bottom: 5px;
}

.focus,
.warn,
.point {
  border-radius: 8px;
  padding: 8px 10px;
  margin: 10px 0;
}

.focus {
  border-left: 4px solid var(--focus);
  background: #132c4c;
}

.warn {
  border-left: 4px solid var(--warn);
  background: #3a2f18;
}

.point {
  border-left: 4px solid var(--ok);
  background: #11322d;
}

body.light .focus {
  background: #eef7ff;
}

body.light .warn {
  background: #fff7e6;
}

body.light .point {
  background: #ecfaf5;
}

details {
  border: 1px solid #355886;
  background: var(--bg-soft);
  border-radius: 10px;
  padding: 8px 10px;
  margin: 8px 0;
}

body.light details {
  border-color: #bdd6f2;
}

summary {
  cursor: pointer;
  font-weight: 700;
}

pre {
  margin: 8px 0 10px;
  padding: 10px;
  overflow: auto;
  border-radius: 8px;
  border: 1px solid #2f4d74;
  background: #0a162a;
  color: #dbe9fb;
}

body.light pre {
  border-color: #c5dbf5;
  background: #f3f9ff;
  color: #1f3550;
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.questions-grid {
  display: grid;
  gap: 9px;
}

.q-block {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-soft);
  padding: 9px 10px;
}

.q-meta {
  margin: 5px 0;
  color: #a8c5e7;
  font-size: 0.82rem;
}

body.light .q-meta {
  color: #4d739b;
}

.q-answer {
  margin-top: 8px;
  border-top: 1px dashed var(--line);
  padding-top: 8px;
}

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.mini-card {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-soft);
  padding: 10px;
}

.mini {
  font-size: 0.88rem;
  color: #c8d8ee;
}

body.light .mini {
  color: #486486;
}

.checklist label {
  display: block;
  padding: 7px 8px;
  margin: 5px 0;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--bg-soft);
}

.quiz {
  display: grid;
  gap: 10px;
  margin-bottom: 12px;
}

.quiz-item {
  border: 1px solid var(--line);
  border-radius: 10px;
  background: var(--bg-soft);
  padding: 10px;
}

.quiz-item label {
  display: block;
  margin: 5px 0;
}

.feedback-list {
  display: grid;
  gap: 8px;
  margin-top: 10px;
}

.feedback {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 9px 10px;
  background: var(--bg-soft);
}

.feedback.ok {
  border-left: 4px solid var(--ok);
}

.feedback.bad {
  border-left: 4px solid var(--danger);
}

.sticky {
  position: fixed;
  right: 14px;
  bottom: 16px;
  text-decoration: none;
  background: #1e8c74;
  color: #fff;
  font-weight: 700;
  font-size: 0.82rem;
  border-radius: 999px;
  padding: 8px 12px;
}

@media (max-width: 900px) {
  .grid-2 {
    grid-template-columns: 1fr;
  }

  .hero-top {
    flex-direction: column;
    align-items: flex-start;
  }
}