:root {
  --bg: #0f1419;
  --panel: #1a212b;
  --panel-2: #222c38;
  --line: #2e3a48;
  --txt: #e8edf2;
  --muted: #93a1b0;
  --accent: #4f9cf9;
  --accent-2: #6fd1c4;
  --ok: #46c98b;
  --bad: #ef6b6b;
  --shadow: 0 8px 28px rgba(0, 0, 0, 0.35);
  --radius: 16px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: "PingFang TC", "Microsoft JhengHei", "Segoe UI", system-ui, sans-serif;
  background: radial-gradient(1200px 600px at 80% -10%, #1d2a3a 0%, var(--bg) 55%);
  color: var(--txt);
  min-height: 100vh;
  line-height: 1.6;
}

/* 頂欄 */
.topbar {
  display: flex; justify-content: space-between; align-items: center;
  padding: 16px 22px; max-width: 860px; margin: 0 auto;
}
.brand { display: flex; gap: 12px; align-items: center; }
.logo { font-size: 30px; }
.brand h1 { font-size: 20px; letter-spacing: 1px; }
.tagline { font-size: 12px; color: var(--muted); }
.key-btn {
  background: var(--panel-2); color: var(--txt); border: 1px solid var(--line);
  padding: 8px 14px; border-radius: 999px; font-size: 13px; cursor: pointer;
  transition: 0.15s;
}
.key-btn:hover { border-color: var(--accent); }
.key-btn.set { border-color: var(--ok); color: var(--ok); }

main { max-width: 860px; margin: 0 auto; padding: 8px 18px 40px; }

.card {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 26px; box-shadow: var(--shadow);
  margin-bottom: 18px;
}
.card h2 { font-size: 19px; margin-bottom: 18px; }

.hidden { display: none !important; }

/* 卷別選擇 */
.papers {
  display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; margin-bottom: 22px;
}
.paper {
  display: flex; flex-direction: column; align-items: flex-start; gap: 2px;
  background: var(--panel-2); border: 1.5px solid var(--line);
  border-radius: 14px; padding: 16px; cursor: pointer; color: var(--txt);
  text-align: left; transition: 0.15s;
}
.paper:hover { border-color: var(--accent); transform: translateY(-2px); }
.paper.active {
  border-color: var(--accent);
  background: linear-gradient(135deg, rgba(79,156,249,0.18), rgba(111,209,196,0.1));
}
.paper-icon {
  font-size: 22px; font-weight: 700; color: var(--accent-2);
  width: 40px; height: 40px; display: grid; place-items: center;
  background: rgba(255,255,255,0.05); border-radius: 10px; margin-bottom: 6px;
}
.paper-name { font-size: 16px; font-weight: 600; }
.paper-sub { font-size: 12px; color: var(--muted); }

/* 選項列 */
.options-row { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 22px; }
.field { display: flex; flex-direction: column; gap: 6px; font-size: 13px; color: var(--muted); }
.field.grow { flex: 1; min-width: 200px; }
.field select, .field input {
  background: var(--panel-2); border: 1px solid var(--line); color: var(--txt);
  padding: 10px 12px; border-radius: 10px; font-size: 14px; outline: none;
}
.field select:focus, .field input:focus { border-color: var(--accent); }

/* 按鈕 */
.primary-btn {
  background: linear-gradient(135deg, var(--accent), #3b7fe0);
  color: #fff; border: none; padding: 13px 22px; border-radius: 12px;
  font-size: 15px; font-weight: 600; cursor: pointer; width: 100%; transition: 0.15s;
}
.primary-btn:hover:not(:disabled) { filter: brightness(1.08); }
.primary-btn:disabled { opacity: 0.45; cursor: not-allowed; }
.ghost-btn {
  background: transparent; color: var(--muted); border: 1px solid var(--line);
  padding: 13px 22px; border-radius: 12px; font-size: 15px; cursor: pointer; width: 100%;
}
.ghost-btn:hover { border-color: var(--accent); color: var(--txt); }

/* 載入 */
#loading { text-align: center; padding: 50px 26px; }
.spinner {
  width: 42px; height: 42px; margin: 0 auto 16px;
  border: 4px solid var(--line); border-top-color: var(--accent);
  border-radius: 50%; animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* 答題 */
.quiz-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 12px; }
.pill {
  background: rgba(79,156,249,0.15); color: var(--accent);
  padding: 4px 12px; border-radius: 999px; font-size: 12px;
}
.progress { font-size: 13px; color: var(--muted); }
.bar { height: 6px; background: var(--panel-2); border-radius: 99px; overflow: hidden; margin-bottom: 22px; }
.bar-fill { height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), var(--accent-2)); transition: width 0.3s; }

.stem { font-size: 17px; line-height: 1.8; margin-bottom: 20px; white-space: pre-wrap; }

.opt-list { display: flex; flex-direction: column; gap: 10px; }
.opt {
  display: flex; gap: 12px; align-items: flex-start;
  background: var(--panel-2); border: 1.5px solid var(--line);
  border-radius: 12px; padding: 14px 16px; cursor: pointer; transition: 0.12s;
}
.opt:hover:not(.locked) { border-color: var(--accent); }
.opt.selected { border-color: var(--accent); background: rgba(79,156,249,0.12); }
.opt.locked { cursor: default; }
.opt.correct { border-color: var(--ok); background: rgba(70,201,139,0.14); }
.opt.wrong { border-color: var(--bad); background: rgba(239,107,107,0.14); }
.opt-label {
  flex-shrink: 0; width: 26px; height: 26px; border-radius: 7px;
  display: grid; place-items: center; font-weight: 700; font-size: 13px;
  background: rgba(255,255,255,0.06); color: var(--accent-2);
}
.opt.correct .opt-label { background: var(--ok); color: #07140d; }
.opt.wrong .opt-label { background: var(--bad); color: #1a0707; }
.opt-text { flex: 1; padding-top: 1px; }

.feedback {
  margin-top: 18px; padding: 16px; border-radius: 12px; font-size: 14px;
  border: 1px solid var(--line); background: var(--panel-2);
}
.feedback.right { border-color: var(--ok); }
.feedback.wrong { border-color: var(--bad); }
.feedback .verdict { font-weight: 700; margin-bottom: 6px; }
.feedback.right .verdict { color: var(--ok); }
.feedback.wrong .verdict { color: var(--bad); }
.feedback .expl { color: var(--muted); white-space: pre-wrap; }

.quiz-foot { margin-top: 22px; }

/* 結算 */
.score { text-align: center; margin: 10px 0; }
#score-num { font-size: 54px; font-weight: 800; color: var(--accent-2); }
.score-total { font-size: 22px; color: var(--muted); }
.score-msg { text-align: center; color: var(--muted); margin-bottom: 22px; }
.review { display: flex; flex-direction: column; gap: 12px; margin-bottom: 22px; }
.rev-item {
  background: var(--panel-2); border: 1px solid var(--line);
  border-left-width: 4px; border-radius: 10px; padding: 14px 16px; font-size: 14px;
}
.rev-item.ok { border-left-color: var(--ok); }
.rev-item.no { border-left-color: var(--bad); }
.rev-q { font-weight: 600; margin-bottom: 6px; }
.rev-a { font-size: 13px; color: var(--muted); }
.rev-a b { color: var(--txt); font-weight: 600; }
.result-foot { display: flex; gap: 12px; }
.result-foot button { flex: 1; }

.footer { text-align: center; color: var(--muted); font-size: 12px; padding: 10px 18px 30px; }

/* Modal */
.modal {
  position: fixed; inset: 0; background: rgba(0,0,0,0.6);
  display: grid; place-items: center; padding: 20px; z-index: 50;
}
.modal-box {
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 24px; max-width: 440px; width: 100%;
  box-shadow: var(--shadow);
}
.modal-box h3 { margin-bottom: 10px; }
.modal-note { font-size: 13px; color: var(--muted); margin-bottom: 14px; }
.modal-box input {
  width: 100%; background: var(--panel-2); border: 1px solid var(--line);
  color: var(--txt); padding: 12px; border-radius: 10px; font-size: 14px;
  outline: none; margin-bottom: 16px;
}
.modal-box input:focus { border-color: var(--accent); }
.modal-foot { display: flex; gap: 10px; }
.modal-foot button { flex: 1; }

@media (max-width: 560px) {
  .papers { grid-template-columns: 1fr; }
  .result-foot { flex-direction: column; }
}