:root {
  --bg: #f4f6fb;
  --card: #ffffff;
  --ink: #1f2733;
  --muted: #6b7787;
  --line: #e3e8f0;
  --primary: #2f6df0;
  --primary-dark: #1f54c4;
  --correct: #1ba672;
  --correct-bg: #e7f7f0;
  --wrong: #e0405a;
  --wrong-bg: #fdeaee;
  --accent: #fff4d6;
  --shadow: 0 6px 24px rgba(31, 39, 51, 0.08);
  --radius: 14px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
}

.site-header {
  background: linear-gradient(120deg, #2f6df0, #5b8def);
  color: #fff;
  padding: 16px 24px;
  box-shadow: var(--shadow);
}
.brand { display: flex; align-items: baseline; gap: 12px; }
.logo {
  font-weight: 800; font-size: 22px; letter-spacing: 1px;
  background: rgba(255, 255, 255, 0.18);
  padding: 2px 10px; border-radius: 8px;
}
.tagline { font-size: 14px; opacity: 0.92; }

main { max-width: 860px; margin: 0 auto; padding: 28px 18px 80px; }

.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 28px;
}

.setup h1 { margin: 0 0 6px; font-size: 26px; }
.lead { color: var(--muted); margin: 0 0 22px; }

.field { margin-bottom: 18px; }
.field label { display: block; font-weight: 600; margin-bottom: 6px; font-size: 14px; }
.field-inline { margin-bottom: 24px; }
select {
  width: 100%; padding: 11px 12px; font-size: 15px;
  border: 1px solid var(--line); border-radius: 10px; background: #fff;
  color: var(--ink);
}
.checkbox { display: inline-flex; align-items: center; gap: 8px; font-weight: 500; cursor: pointer; }
.checkbox input { width: 18px; height: 18px; }

.btn {
  border: none; cursor: pointer; border-radius: 10px;
  font-size: 15px; font-weight: 600; padding: 12px 20px;
  transition: transform 0.05s ease, background 0.15s ease;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-lg { width: 100%; padding: 14px; font-size: 16px; }
.btn-ghost { background: #eef2f9; color: var(--ink); }
.btn-ghost:hover { background: #e2e8f3; }
.btn:disabled { opacity: 0.55; cursor: not-allowed; }

.error { color: var(--wrong); margin-top: 12px; font-size: 14px; }

/* Summary */
.summary {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 22px 24px; margin-bottom: 22px; text-align: center;
}
.summary h2 { margin: 0 0 4px; font-size: 22px; }
.score { font-size: 40px; font-weight: 800; color: var(--primary); }
.score small { font-size: 18px; color: var(--muted); font-weight: 600; }
.summary .meta { color: var(--muted); margin-top: 6px; }

/* Progress bar */
.progress-wrap {
  position: sticky; top: 12px; z-index: 5;
  background: var(--card); border: 1px solid var(--line); border-radius: 999px;
  height: 34px; display: flex; align-items: center; overflow: hidden;
  box-shadow: var(--shadow); margin-bottom: 22px; position: relative;
}
.progress-fill {
  height: 100%; width: 0%; background: linear-gradient(90deg, #2f6df0, #5b8def);
  transition: width 0.25s ease;
}
.progress-text {
  position: absolute; left: 50%; transform: translateX(-50%);
  font-size: 13px; font-weight: 600; color: var(--ink);
}

/* Question card */
.q-card {
  background: var(--card); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 22px 24px; margin-bottom: 18px; border: 2px solid transparent;
}
.q-card.correct { border-color: var(--correct); }
.q-card.wrong { border-color: var(--wrong); }
.q-head { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.q-num {
  background: var(--primary); color: #fff; font-weight: 700; font-size: 13px;
  min-width: 28px; height: 28px; border-radius: 8px; display: grid; place-items: center;
}
.q-badge {
  font-size: 12px; font-weight: 700; padding: 2px 10px; border-radius: 999px;
}
.q-badge.ok { background: var(--correct-bg); color: var(--correct); }
.q-badge.no { background: var(--wrong-bg); color: var(--wrong); }

.q-stem { font-size: 16px; margin: 6px 0 16px; white-space: pre-wrap; }

.option {
  display: flex; align-items: flex-start; gap: 12px;
  padding: 11px 13px; border: 1px solid var(--line); border-radius: 10px;
  margin-bottom: 10px; cursor: pointer; transition: background 0.12s ease, border-color 0.12s ease;
}
.option:hover { background: #f7f9fd; }
.option input { margin-top: 4px; width: 18px; height: 18px; flex: none; }
.option .opt-text { flex: 1; }
.option .opt-letter {
  font-weight: 700; color: var(--primary); flex: none;
  min-width: 20px;
}
.option.opt-correct { background: var(--correct-bg); border-color: var(--correct); }
.option.opt-wrong { background: var(--wrong-bg); border-color: var(--wrong); }
.option.opt-dim { opacity: 0.6; }

.explanation {
  margin-top: 12px; padding: 14px 16px; background: #f8fafc;
  border-left: 4px solid var(--primary); border-radius: 8px; font-size: 14px;
}
.explanation h4 { margin: 0 0 8px; font-size: 13px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.5px; }
.explanation .exp-item { margin-bottom: 4px; }
.explanation .exp-item.is-correct { color: var(--correct); font-weight: 600; }
.explanation .exp-item.is-wrong { color: var(--wrong); }
.refs { margin-top: 10px; font-size: 13px; color: var(--muted); }
.refs code { background: #eef2f9; padding: 1px 6px; border-radius: 5px; }

.action-bar {
  display: flex; gap: 12px; flex-wrap: wrap; margin-top: 8px;
}
.action-bar .btn-primary { flex: 1; min-width: 160px; }

.site-footer {
  text-align: center; color: var(--muted); font-size: 13px; padding: 20px;
}
.site-footer code { background: #eef2f9; padding: 1px 6px; border-radius: 5px; }

@media (max-width: 560px) {
  .action-bar .btn { width: 100%; }
}