:root {
  --space-bg-0: #141629;
  --space-bg-1: #1a2145;
  --space-card: rgba(22, 28, 56, 0.78);
  --space-border: rgba(255, 213, 106, 0.25);
  --space-accent: #ffd56a;
  --space-accent-2: #7ee2ff;
  --space-text: #b8c6dc;
  --space-muted: #9fb0cf;
  --space-warn: #ffe3e3;
  --space-warn-border: #f4c7c7;
}

body {
  font-family: "Microsoft YaHei", "PingFang SC", "SimSun", sans-serif;
  background: radial-gradient(1200px 600px at 20% 10%, #27305e 0%, transparent 60%),
              radial-gradient(900px 500px at 80% 20%, #2a2757 0%, transparent 60%),
              linear-gradient(160deg, var(--space-bg-0), var(--space-bg-1));
  margin: 0;
  color: var(--space-text);
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
}

body::before,
body::after {
  content: "";
  position: fixed;
  inset: 0;
  background-image: radial-gradient(#ffffff 1px, transparent 1px);
  background-size: 70px 70px;
  opacity: 0.1;
  pointer-events: none;
  z-index: 0;
}

body::after {
  background-size: 140px 140px;
  opacity: 0.05;
}

.site-header {
  background: rgba(20, 26, 49, 0.88);
  padding: 16px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid rgba(255, 213, 106, 0.2);
  position: sticky;
  top: 0;
  z-index: 5;
  backdrop-filter: blur(6px);
}

.site-header h1 {
  font-family: "Microsoft YaHei", "PingFang SC", "SimSun", sans-serif;
  margin: 0;
  color: var(--space-accent);
}

.site-header nav a {
  margin-left: 16px;
  text-decoration: none;
}

.nav-link {
  background: transparent;
  border: 1px solid rgba(184, 198, 220, 0.35);
  color: var(--space-text);
  padding: 6px 10px;
  border-radius: 10px;
  font-size: 14px;
}

.nav-link:hover {
  border-color: rgba(255, 213, 106, 0.6);
  color: var(--space-accent);
}

.nav-link.active {
  border-color: rgba(255, 213, 106, 0.85);
  color: var(--space-accent);
  box-shadow: 0 0 0 1px rgba(255, 213, 106, 0.2);
}

.nav-logout-form {
  display: inline;
  margin-left: 12px;
}

.nav-logout-btn {
  background: transparent;
  cursor: pointer;
}

.nav-logout-btn:hover {
  border-color: rgba(255, 213, 106, 0.6);
  color: var(--space-accent);
}

.flash-wrapper { display:grid; grid-template-columns: 2fr 1fr; gap:20px; align-items:start; }
.flash-card { background:var(--space-card); border:1px solid var(--space-border); border-radius:18px; padding:20px; box-shadow:0 12px 30px rgba(0,0,0,.35); }
.card-top { display:flex; justify-content:space-between; align-items:center; }
.tag { padding:4px 10px; border-radius:12px; border:1px solid var(--space-accent-2); color:var(--space-accent-2); }
.timer { font-family: "JetBrains Mono", monospace; }
.expr {
  font-size: 26px;
  margin: 18px 0 10px;
  color: #fff;
  text-shadow: 0 0 12px rgba(122,226,255,.5);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

@media (max-width: 520px) {
  .expr { font-size: 22px; }
}
.meta { color:var(--space-muted); margin-bottom:12px; }
.actions { display:flex; gap:10px; align-items:center; margin-bottom:12px; }
.answer { flex:1; padding:12px 14px; border-radius:12px; border:1px solid #2c3b64; background:#0f162c; color:#fff; }
.primary { background:var(--space-accent-2); color:#031622; border:none; padding:12px 16px; border-radius:12px; font-weight:700; cursor:pointer; box-shadow:0 0 16px rgba(122,226,255,.5); }
.ghost { background:transparent; color:var(--space-accent-2); border:1px solid var(--space-accent-2); padding:10px 14px; border-radius:12px; cursor:pointer; }
.progress { height:8px; background:#1b2948; border-radius:8px; overflow:hidden; }
.progress div { height:100%; background:linear-gradient(90deg, #72ffb4, #5ae6ff); transition:width .1s linear; }
.side-panel .panel { background:var(--space-card); border:1px solid #23325c; border-radius:14px; padding:14px 16px; margin-bottom:12px; }
.toast { margin-top:10px; padding:8px 10px; border-radius:10px; background:#1f2b4c; border:1px solid #304070; color:#fff; }
.toast[data-tone="success"] { border-color:#72ffb4; color:#72ffb4; }
.toast[data-tone="warn"] { border-color:#ffb347; color:#ffb347; }
.toast[data-tone="error"] { border-color:#ff6b6b; color:#ff6b6b; }

.container {
  max-width: 980px;
  margin: 24px auto;
  padding: 0 16px 60px;
  position: relative;
  z-index: 1;
}

input[type="text"] {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid rgba(126, 226, 255, 0.3);
  border-radius: 8px;
  background: rgba(14, 20, 42, 0.7);
  color: var(--space-text);
  font-size: 20px;
}

textarea {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid rgba(126, 226, 255, 0.3);
  border-radius: 8px;
  background: rgba(14, 20, 42, 0.7);
  color: var(--space-text);
  font-size: 18px;
}

select {
  padding: 10px 12px;
  border-radius: 8px;
  border: 1px solid rgba(126, 226, 255, 0.3);
  background: rgba(14, 20, 42, 0.7);
  color: var(--space-text);
}

.btn {
  display: inline-block;
  margin-top: 12px;
  padding: 10px 16px;
  background: linear-gradient(120deg, var(--space-accent), var(--space-accent-2));
  color: #111827;
  text-decoration: none;
  border-radius: 10px;
  border: none;
  font-weight: 700;
}

.btn.btn-secondary {
  background: rgba(255, 213, 106, 0.15);
  color: var(--space-accent);
  border: 1px solid rgba(255, 213, 106, 0.35);
}

table {
  width: 100%;
  border-collapse: collapse;
  background: var(--space-card);
  margin-top: 12px;
  border: 1px solid var(--space-border);
  border-radius: 12px;
  overflow: hidden;
}

table th, table td {
  border: 1px solid rgba(255, 213, 106, 0.12);
  padding: 10px 12px;
  text-align: left;
  color: var(--space-text);
}

.submission-card {
  background: var(--space-card);
  border: 1px solid var(--space-border);
  border-radius: 16px;
  padding: 16px;
  margin-bottom: 16px;
  box-shadow: 0 18px 50px rgba(9, 12, 28, 0.45);
}

.submission-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  color: var(--space-text);
}

.submission-header .score {
  font-weight: 600;
  color: var(--space-accent);
}

.submission-meta {
  color: var(--space-muted);
  margin-bottom: 8px;
}

.row-wrong {
  background: #fef2f2;
}

.question-card {
  background: rgba(20, 26, 54, 0.75);
  padding: 12px 16px;
  margin-bottom: 12px;
  border-radius: 12px;
  border: 1px solid rgba(126, 226, 255, 0.18);
}

.question-card.wrong {
  background: var(--space-warn);
  border-color: var(--space-warn-border);
  color: #5b1f1f;
}

.q-title {
  font-weight: 700;
  margin-bottom: 10px;
  font-size: 24px;
  line-height: 1.55;
}

.choices {
  display: grid;
  gap: 6px;
  margin-bottom: 8px;
}

.choice-item {
  display: flex;
  align-items: center;
  gap: 8px;
}

.answer-box {
  margin-top: 6px;
  padding: 4px 0;
}

.answer-correct {
  color: #9bdcff;
  font-weight: 600;
}

.answer-wrong {
  color: #9bdcff;
  font-weight: 600;
}

.explain-link {
  margin-left: 12px;
  font-size: 13px;
  color: var(--space-muted);
}

.exam-controls {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.timer-box {
  background: rgba(14, 20, 42, 0.75);
  border: 1px solid rgba(255, 213, 106, 0.25);
  border-radius: 10px;
  padding: 6px 12px;
}

.warn-banner {
  margin: 12px 0 4px;
  padding: 10px 14px;
  border-radius: 12px;
  background: rgba(255, 213, 106, 0.16);
  border: 1px solid rgba(255, 213, 106, 0.4);
  color: var(--space-text);
  font-weight: 600;
}

.exam-grid {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}

.exam-card {
  background: var(--space-card);
  border: 1px solid var(--space-border);
  border-radius: 16px;
  padding: 18px;
  box-shadow: 0 16px 40px rgba(9, 12, 28, 0.4);
}

.exam-title {
  font-family: "Microsoft YaHei", "PingFang SC", "SimSun", sans-serif;
  font-size: 18px;
  color: var(--space-accent);
  margin-bottom: 8px;
}

.exam-meta {
  color: var(--space-muted);
}

.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 999;
}

.overlay.hidden {
  display: none;
}

.overlay-card {
  background: rgba(14, 20, 42, 0.92);
  padding: 20px 24px;
  border-radius: 14px;
  width: 320px;
  text-align: center;
  border: 1px solid rgba(255, 213, 106, 0.25);
  color: var(--space-text);
}

.explain {
  background: rgba(14, 20, 42, 0.9);
  color: var(--space-text);
  padding: 16px;
  border-radius: 8px;
  white-space: pre-wrap;
  border: 1px solid rgba(126, 226, 255, 0.2);
}

.note-board {
  background: var(--space-card);
  border: 1px solid var(--space-border);
  border-radius: 18px;
  padding: 24px;
  box-shadow: 0 18px 50px rgba(9, 12, 28, 0.45);
  position: relative;
  overflow: hidden;
}

.note-board::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: repeating-linear-gradient(
    to bottom,
    rgba(255, 213, 106, 0.06),
    rgba(255, 213, 106, 0.06) 1px,
    transparent 1px,
    transparent 24px
  );
  pointer-events: none;
}

.note-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: relative;
  z-index: 1;
}

.note-title {
  font-family: "ZCOOL KuaiLe", cursive;
  font-size: 28px;
  margin: 0 0 6px;
  color: var(--space-accent);
}

.note-subtitle {
  margin: 0;
  color: var(--space-muted);
}

.note-tag {
  background: rgba(255, 213, 106, 0.2);
  color: var(--space-accent);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
}

.note-paper {
  position: relative;
  z-index: 1;
  margin-top: 16px;
  background: rgba(14, 20, 42, 0.7);
  border: 1px dashed rgba(126, 226, 255, 0.3);
  border-radius: 14px;
  padding: 18px 20px;
}

.markdown-body h1,
.markdown-body h2,
.markdown-body h3 {
  font-family: "ZCOOL KuaiLe", cursive;
  color: var(--space-accent);
}

.markdown-body p {
  line-height: 1.7;
  color: var(--space-text);
}

.markdown-body ul {
  padding-left: 20px;
}

.markdown-body blockquote {
  background: rgba(126, 226, 255, 0.12);
  border-left: 4px solid rgba(126, 226, 255, 0.5);
  margin: 12px 0;
  padding: 8px 12px;
  color: var(--space-text);
}

.quiz-board {
  margin-top: 24px;
  background: var(--space-card);
  border-radius: 16px;
  padding: 20px;
  border: 1px solid var(--space-border);
}

.quiz-title {
  margin: 0 0 12px;
  color: var(--space-accent);
}

.quiz-item {
  margin-bottom: 12px;
}

.quiz-question {
  font-weight: 600;
  margin-bottom: 6px;
}

.quiz-result {
  margin-top: 16px;
  background: rgba(14, 20, 42, 0.7);
  padding: 12px;
  border-radius: 10px;
  border: 1px solid rgba(126, 226, 255, 0.2);
}

.quiz-result .ok {
  color: #166534;
}

.quiz-result .bad {
  color: #b91c1c;
}

@media (max-width: 900px) {
  .container { padding: 10px; }
  nav { flex-wrap: wrap; }
  .flash-wrapper { grid-template-columns: 1fr; }
}