/* ============================================================
   回见 · 样式（移动端优先，桌面居中，支持深色模式）
   ============================================================ */
:root {
  --bg: #f4f5fa;
  --card: #ffffff;
  --ink: #1b1f2b;
  --ink2: #74798c;
  --line: #e7e9f2;
  --primary: #4361ee;
  --primary-soft: #e8ecff;
  --green: #0fa367;
  --amber: #d97c00;
  --red: #e03e44;
  --shadow: 0 6px 24px rgba(28, 32, 58, .08);
  --nav-h: 58px;
  --radius: 16px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12141d;
    --card: #1d2130;
    --ink: #e9ebf5;
    --ink2: #9aa0b5;
    --line: #2b3042;
    --primary: #6f8bff;
    --primary-soft: #232b4d;
    --green: #1db87a;
    --amber: #f0a02d;
    --done-ink: #10142a;
    --shadow: 0 6px 24px rgba(0,0,0,.4);
  }
  /* 暗色下压暗评分按钮底色，保证白字对比度 ≥3:1 */
  .grade-fuzzy { background: #b87300; }
  .grade-know { background: #0e8f5c; }
}

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
.btn-primary, .grade, .tab, .spk, .mini-btn, .card3d, .pack-head { touch-action: manipulation; }
html, body { margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei",
               "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--ink);
  height: 100%;
  max-width: 100%;
  overscroll-behavior-y: none;
  -webkit-user-select: none; user-select: none;
}
main { padding: 0; }
.hidden { display: none !important; }

/* ---------- 顶栏 ---------- */
.topbar {
  position: sticky; top: 0; z-index: 30;
  background: var(--bg);
  padding: max(10px, env(safe-area-inset-top)) 16px 8px;
}
.topbar-in { max-width: 520px; margin: 0 auto; display: flex; align-items: center; justify-content: space-between; }
.brand { display: flex; align-items: center; gap: 8px; color: var(--primary); }
.brand-name { font-size: 19px; font-weight: 800; letter-spacing: .5px; color: var(--ink); }
.brand-sub { font-size: 12px; color: var(--ink2); }
.top-right { display: flex; align-items: center; gap: 10px; }
.today-line { font-size: 12.5px; color: var(--ink2); }
.streak-badge { font-size: 13px; font-weight: 700; color: var(--amber); background: color-mix(in srgb, var(--amber) 15%, transparent); padding: 3px 10px; border-radius: 999px; }

/* ---------- 内容 ---------- */
.content { max-width: 520px; margin: 0 auto; padding: 4px 16px calc(var(--nav-h) + env(safe-area-inset-bottom) + 26px); }
.view > * { margin-top: 14px; }

/* ---------- 学习页 ---------- */
#taskRing { stroke: var(--primary); transition: stroke-dashoffset .4s; }
#taskRingBg { stroke: var(--line); }
.task-card {
  background: var(--card); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 18px 18px 14px;
}
.task-title { font-size: 15px; font-weight: 700; margin-bottom: 12px; }
.task-ring-wrap { position: relative; width: 104px; margin: 4px auto 6px; }
.task-ring-text {
  position: absolute; inset: 0; display: flex; align-items: center; justify-content: center;
  gap: 2px; font-size: 13px; color: var(--ink2);
}
.task-ring-text b { font-size: 24px; color: var(--ink); }
.task-rows { margin-top: 10px; }
.task-row {
  display: flex; align-items: center; gap: 8px;
  font-size: 15px; padding: 9px 4px;
  border-top: 1px solid var(--line);
}
.task-dot { width: 10px; height: 10px; border-radius: 3px; }
.dot-new { background: var(--primary); }
.dot-rev { background: var(--red); }
.task-row b { margin-left: auto; font-size: 17px; }
.task-row-sub { font-size: 12px; color: var(--ink2); margin-left: auto; font-weight: 400; }
#rowRev.warn { color: var(--red); }
.task-backlog { font-size: 12.5px; color: var(--ink2); text-align: center; padding-top: 8px; }

.btn-primary {
  appearance: none; border: 0; width: 100%;
  background: var(--primary); color: #fff;
  font-size: 17px; font-weight: 700;
  min-height: 54px; border-radius: 14px;
  box-shadow: 0 8px 20px color-mix(in srgb, var(--primary) 35%, transparent);
  cursor: pointer;
}
.btn-primary:active { transform: scale(.98); }
.btn-primary:disabled { background: var(--ink2); box-shadow: none; opacity: .6; }
.btn-big { min-height: 58px; font-size: 18px; }
.study-hint { text-align: center; font-size: 13px; color: var(--ink2); margin: 8px 0 0; }

/* ---------- 复习页 / 通用列表 ---------- */
.view-head { display: flex; align-items: baseline; justify-content: space-between; }
.view-head h2 { font-size: 20px; margin: 0; }
.view-head-sub { font-size: 12.5px; color: var(--ink2); }
.switch-row { display: flex; align-items: center; gap: 8px; font-size: 14px; color: var(--ink2); padding: 10px 0; }
.switch-row input { width: 18px; height: 18px; accent-color: var(--primary); }
.list { display: flex; flex-direction: column; gap: 8px; }
.list-item {
  background: var(--card); border-radius: 12px; padding: 10px 12px;
  display: flex; align-items: center; gap: 10px; box-shadow: var(--shadow);
}
.list-item .li-word { font-size: 16px; font-weight: 700; min-width: 110px; }
.list-item .li-cn { font-size: 13px; color: var(--ink2); flex: 1; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.tag { font-size: 11px; padding: 2px 7px; border-radius: 999px; white-space: nowrap; }
.tag-wrong { color: var(--red); background: color-mix(in srgb, var(--red) 14%, transparent); }
.tag-fuzzy { color: var(--amber); background: color-mix(in srgb, var(--amber) 15%, transparent); }
.tag-due { color: var(--primary); background: var(--primary-soft); }
.empty-state { text-align: center; color: var(--ink2); font-size: 14px; padding: 36px 0; }

/* ---------- 词表页 ---------- */
.packs { display: flex; flex-direction: column; gap: 8px; }
.pack-card { background: var(--card); border-radius: 12px; box-shadow: var(--shadow); overflow: hidden; }
.pack-head {
  display: flex; align-items: center; gap: 10px; padding: 12px 14px; cursor: pointer;
}
.pack-head.open { background: var(--primary-soft); }
.pack-no { font-size: 14px; font-weight: 700; color: var(--primary); background: var(--card); border-radius: 8px; padding: 2px 8px; }
.pack-name { font-weight: 700; font-size: 15px; flex: 1; }
.pack-meta { font-size: 12px; color: var(--ink2); display: flex; align-items: center; gap: 8px; }
.pack-bar { width: 52px; height: 6px; background: var(--line); border-radius: 3px; overflow: hidden; }
.pack-bar i { display: block; height: 100%; background: var(--green); }
.pack-done { color: var(--green); font-weight: 700; }
.pack-cur { outline: 2px solid color-mix(in srgb, var(--primary) 55%, transparent); }
.pack-body { border-top: 1px solid var(--line); max-height: 46vh; overflow: auto; }
.pack-word {
  display: flex; align-items: center; gap: 8px; padding: 7px 14px;
  font-size: 13.5px; border-top: 1px solid var(--line);
}
.pack-word:first-child { border-top: 0; }
.pw-spell { font-weight: 600; min-width: 92px; }
.pw-ph { color: var(--ink2); font-size: 12px; min-width: 108px; }
.pw-cn { color: var(--ink2); flex: 1; }
.mini-btn {
  border: 0; font-size: 12.5px; padding: 8px 12px; margin: -4px -2px; border-radius: 8px;
  background: var(--primary-soft); color: var(--primary); cursor: pointer; white-space: nowrap;
}
.mini-btn:disabled { opacity: .4; }
.mini-btn:active, .spk:active { transform: scale(.93); filter: brightness(.92); }

/* ---------- 统计页 ---------- */
.cal-card { background: var(--card); border-radius: var(--radius); padding: 14px; box-shadow: var(--shadow); }
.cal-title { font-size: 14px; font-weight: 700; margin-bottom: 10px; text-align: center; }
.cal-grid { display: grid; grid-template-columns: repeat(7, 1fr); gap: 4px; text-align: center; }
.cal-wd { font-size: 11px; color: var(--ink2); padding: 3px 0; }
.cal-cell {
  min-height: 34px;                    /* 无 aspect-ratio 的老内核回退 */
  aspect-ratio: 1; display: flex; align-items: center; justify-content: center;
  font-size: 12.5px; color: var(--ink2); border-radius: 8px;
}
.cal-cell.done { color: var(--done-ink, #fff); background: var(--primary); font-weight: 700; }
.cal-cell.today { outline: 2px solid var(--green); outline-offset: -2px; color: var(--ink); font-weight: 700; }
.stat-cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }
.stat-card { background: var(--card); border-radius: 12px; padding: 14px 8px; text-align: center; box-shadow: var(--shadow); }
.stat-num { font-size: 24px; font-weight: 800; color: var(--primary); }
.stat-label { font-size: 12px; color: var(--ink2); margin-top: 4px; }

/* ---------- 全屏学习态 ---------- */
.study {
  position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 60;
  background: var(--bg);
  display: flex; flex-direction: column;
  padding: max(10px, env(safe-area-inset-top)) 16px calc(12px + env(safe-area-inset-bottom));
}
.study-top { display: flex; align-items: center; gap: 10px; width: 100%; max-width: 520px; margin: 0 auto; }
.study-mode { font-size: 13px; font-weight: 700; color: var(--primary); background: var(--primary-soft); padding: 3px 10px; border-radius: 999px; }
.study-progress { flex: 1; height: 8px; background: var(--line); border-radius: 4px; overflow: hidden; }
#studyProgressBar { height: 100%; width: 0; background: linear-gradient(90deg, var(--primary), #8fa3ff); transition: width .25s; border-radius: 4px; }
.study-remain { font-size: 12.5px; color: var(--ink2); min-width: 38px; text-align: right; }

.stage { flex: 1; display: flex; align-items: center; justify-content: center; min-height: 0; padding: 6px 0; }
.card3d {
  width: 100%; max-width: 420px;
  perspective: 1000px;
  transition: transform .22s ease, opacity .22s ease;
}
.card3d.out-left { transform: translateX(-110%) rotate(-6deg); opacity: 0; }
.card3d.out-right { transform: translateX(110%) rotate(6deg); opacity: 0; }
.card3d.shake { animation: shake .35s; }
@keyframes shake {
  0%,100% { transform: translateX(0); }
  25% { transform: translateX(-10px); }
  50% { transform: translateX(8px); }
  75% { transform: translateX(-6px); }
}
.card-inner { position: relative; transform-style: preserve-3d; transition: transform .3s ease; }
.card-inner.flipped { transform: rotateY(180deg); }
.face {
  backface-visibility: hidden; -webkit-backface-visibility: hidden;
  background: var(--card); border-radius: 20px; box-shadow: var(--shadow);
  min-height: 320px;                    /* 老内核无 clamp() 的回退 */
  min-height: clamp(320px, 52vh, 430px);
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 12px;
  padding: 24px; text-align: center;
}
.face.back { position: absolute; top: 0; right: 0; bottom: 0; left: 0; transform: rotateY(180deg); }
.face.back { justify-content: flex-start; padding-top: 96px; box-shadow: var(--shadow); }

.no-speak .spk { display: none; }

.front-tip { position: absolute; top: 18px; font-size: 12.5px; color: var(--ink2); }
.front-word { font-size: clamp(30px, 9vw, 44px); font-weight: 800; letter-spacing: .5px; word-break: break-all; }
.front-ph { font-size: 16px; color: var(--ink2); }
.spk { border: 0; background: var(--primary-soft); color: var(--primary); font-size: 17px; width: 46px; height: 46px; border-radius: 50%; cursor: pointer; }
.face.back .spk { position: absolute; top: 18px; right: 18px; }

.back-word { font-size: 22px; font-weight: 700; }
.back-pos { font-size: 12px; color: var(--ink2); background: var(--line); padding: 2px 9px; border-radius: 999px; }
.back-cn { font-size: clamp(19px, 5.6vw, 26px); font-weight: 700; color: var(--primary); line-height: 1.5; }

.grade-row { display: grid; grid-template-columns: 1fr 1fr 1.2fr; gap: 10px; margin: 10px auto 6px; width: 100%; max-width: 520px; }
.grade { border: 0; height: 58px; border-radius: 14px; font-size: 17px; font-weight: 700; color: #fff; cursor: pointer; transition: transform .1s, opacity .15s; }
.grade:disabled { opacity: .25; pointer-events: none; }
.grade:active { transform: scale(.96); }
.grade-forget { background: var(--red); }
.grade-fuzzy { background: var(--amber); }
.grade-know { background: var(--green); font-size: 18px; }
.study-quit { border: 0; background: none; color: var(--ink2); font-size: 13px; margin: 4px auto 0; width: 100%; max-width: 520px; padding: 12px 0; }

/* ---------- 打卡页 ---------- */
.checkin { position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 80; background: rgba(10,12,22,.55); backdrop-filter: blur(4px); display: flex; align-items: center; justify-content: center; padding: 24px; }
.checkin-box { background: var(--card); border-radius: 22px; width: 100%; max-width: 360px; padding: 28px 22px; text-align: center; box-shadow: var(--shadow); }
.checkin-emoji { font-size: 46px; }
.checkin-title { font-size: 22px; font-weight: 800; margin: 10px 0 16px; }
.checkin-rows { display: flex; flex-direction: column; gap: 8px; margin-bottom: 18px; }
.ci-row { font-size: 14px; color: var(--ink2); display: flex; justify-content: space-between; padding: 7px 12px; background: var(--bg); border-radius: 10px; }
.ci-row b { color: var(--ink); font-size: 15px; }

/* ---------- 底部导航 ---------- */
.tabbar {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 40;
  height: calc(var(--nav-h) + env(safe-area-inset-bottom));
  padding-bottom: env(safe-area-inset-bottom);
  background: var(--card);
  background: color-mix(in srgb, var(--card) 92%, transparent);
  backdrop-filter: blur(14px); -webkit-backdrop-filter: blur(14px);
  border-top: 1px solid var(--line);
  display: flex;
  max-width: 520px; margin: 0 auto;
}
.tab {
  flex: 1; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 2px;
  text-decoration: none; color: var(--ink2); font-size: 11px; font-weight: 600;
  min-height: 48px; position: relative;
}
.tab.active { color: var(--primary); }
.nav-badge {
  position: absolute; top: 2px; right: calc(50% - 34px);
  background: var(--red); color: #fff; font-size: 10px; font-weight: 700;
  min-width: 16px; height: 16px; line-height: 16px; padding: 0 4px;
  border-radius: 999px; text-align: center;
}

/* ---------- 其它 ---------- */
.toast { position: fixed; left: 50%; transform: translateX(-50%); bottom: calc(var(--nav-h) + env(safe-area-inset-bottom) + 20px); z-index: 90; background: rgba(20,24,40,.92); color: #fff; font-size: 13px; padding: 9px 16px; border-radius: 999px; max-width: 88vw; text-align: center; }

@media (orientation: landscape) and (max-height: 500px) {
  .face { min-height: 230px; }
  .face.back { padding-top: 56px; }
}
.fatal { position: fixed; top: 0; right: 0; bottom: 0; left: 0; z-index: 99; display: flex; align-items: center; justify-content: center; padding: 24px; background: var(--bg); }
.fatal-box { font-size: 15px; color: var(--ink); }
code { background: var(--line); padding: 1px 5px; border-radius: 4px; }

@media (min-width: 760px) {
  .topbar-in, .content { padding-left: 20px; padding-right: 20px; }
  .face { min-height: 400px; }
}

/* ============================================================
   数学模块
   ============================================================ */
.ch-row {
  background: var(--card); border-radius: 12px; padding: 10px 12px;
  display: flex; align-items: center; gap: 10px; box-shadow: var(--shadow);
}
.wk-badge {
  font-size: 11px; font-weight: 700; color: var(--amber); white-space: nowrap;
  background: var(--line); background: color-mix(in srgb, var(--amber) 15%, transparent);
  padding: 3px 8px; border-radius: 999px;
}
.ch-main { flex: 1; min-width: 0; }
.ch-name { font-size: 14.5px; font-weight: 700; }
.ch-sub { font-size: 12px; color: var(--ink2); margin-top: 2px; }
#mathStreak { float: none; }
.task-row .task-row-sub { margin-left: auto; }

/* 数学卡片：正面题目/背面解析，内容可长，需可滚动 */
#mFront { justify-content: center; overflow-y: auto; gap: 10px; }
#mBack { justify-content: flex-start; padding-top: 24px; gap: 10px; overflow-y: auto; text-align: left; }
.m-badges { display: flex; gap: 8px; justify-content: center; flex-wrap: wrap; }
.m-title { font-size: clamp(22px, 6vw, 30px); font-weight: 800; line-height: 1.4; }
.m-hint { font-size: 13.5px; color: var(--ink2); line-height: 1.8; margin-top: 4px; }
.m-stem {
  font-size: 16.5px; font-weight: 600; line-height: 1.8;
  text-align: left; word-break: break-word; white-space: pre-wrap; width: 100%;
}
.m-opts { display: flex; flex-direction: column; gap: 8px; width: 100%; margin-top: 8px; }
.m-opt {
  border: 1.5px solid var(--line); background: var(--card); color: var(--ink);
  border-radius: 10px; padding: 11px 12px; font-size: 14.5px; text-align: left;
  cursor: pointer; line-height: 1.55; word-break: break-word;
  touch-action: manipulation; -webkit-tap-highlight-color: transparent;
}
.m-opt:disabled { cursor: default; }
.m-opt.correct { border-color: var(--green); background: var(--primary-soft); background: color-mix(in srgb, var(--green) 12%, var(--card)); font-weight: 700; }
.m-opt.wrong { border-color: var(--red); background: color-mix(in srgb, var(--red) 10%, var(--card)); }
.m-reveal { margin-top: 10px; align-self: center; }
.m-ans { font-size: 16px; font-weight: 700; line-height: 1.7; word-break: break-word; }
.m-sec { background: var(--bg); border-radius: 12px; padding: 10px 12px; }
.m-sec-t { font-size: 12px; font-weight: 800; color: var(--primary); margin-bottom: 4px; }
.m-sec-b { font-size: 14px; line-height: 1.7; word-break: break-word; }
.m-refs { font-size: 11.5px; color: var(--ink2); text-align: right; }
#mGradeRow.q-mode { grid-template-columns: 1fr 1fr; }
#mGradeRow.q-mode .grade-know { font-size: 17px; }