/* ==================== Java系统设计面试陪练 · 手机优先样式 ==================== */
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

:root {
  --bg: #f2f5fa;
  --card: #ffffff;
  --ink: #1e293b;
  --ink2: #64748b;
  --line: #e2e8f0;
  --pri: #2563eb;
  --pri-ink: #ffffff;
  --ghost: #eef2ff;
  --ghost-ink: #4338ca;
  --badge: #fef3c7;
  --badge-ink: #92400e;
  --term: #0e7490;
  --code-bg: #0f172a;
  --code-ink: #e2e8f0;
  --sheet-shadow: 0 -8px 40px rgba(15, 23, 42, .18);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1220;
    --card: #151e31;
    --ink: #e6ecf7;
    --ink2: #8ea0bd;
    --line: #253147;
    --pri: #3b82f6;
    --ghost: #1e2a4a;
    --ghost-ink: #a5b4fc;
    --badge: #3b2f10;
    --badge-ink: #fcd34d;
    --term: #22d3ee;
    --sheet-shadow: 0 -8px 40px rgba(0, 0, 0, .55);
  }
}

html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.65;
  padding: env(safe-area-inset-top) env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left);
}

.wrap { max-width: 780px; margin: 0 auto; padding: 12px 14px 40px; }

/* ---------- 顶栏 ---------- */
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 10px; padding: 10px 2px 14px; flex-wrap: wrap; }
.brand { display: flex; align-items: center; gap: 10px; }
.logo { font-size: 30px; }
.brand h1 { font-size: 19px; margin: 0; }
.sub { margin: 0; font-size: 12px; color: var(--ink2); }
.model-row { display: flex; align-items: center; gap: 6px; font-size: 13px; color: var(--ink2); }
.model-row select, .model-row input {
  max-width: 250px; padding: 7px 8px; border-radius: 9px;
  border: 1px solid var(--line); background: var(--card); color: var(--ink); font-size: 13px;
}

/* ---------- 难度页签 ---------- */
.levels { display: flex; gap: 8px; margin-bottom: 14px; }
.lv {
  flex: 1; padding: 11px 0; border: 1px solid var(--line); border-radius: 12px;
  background: var(--card); color: var(--ink2); font-size: 15px; font-weight: 600; cursor: pointer;
}
.lv.active { background: var(--pri); border-color: var(--pri); color: var(--pri-ink); box-shadow: 0 4px 14px rgba(37, 99, 235, .35); }

/* ---------- 卡片 ---------- */
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: 16px;
  padding: 20px 18px; box-shadow: 0 2px 12px rgba(15, 23, 42, .05);
  animation: pop .25s ease;
}
@keyframes pop { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
.hidden { display: none !important; }

.idle { text-align: center; padding: 40px 18px; }
.idle-emoji { font-size: 46px; margin-bottom: 8px; }
.idle p { color: var(--ink2); margin: 6px 0 18px; }
.hint { font-size: 12.5px; color: var(--ink2); margin-top: 12px; }

/* ---------- 题目 ---------- */
.q-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 10px; }
.badge { background: var(--badge); color: var(--badge-ink); font-size: 12px; font-weight: 700; padding: 3px 10px; border-radius: 999px; }
.q-count { font-size: 12px; color: var(--ink2); }
.q-title { font-size: 21px; margin: 4px 0 8px; line-height: 1.4; }
.q-desc { color: var(--ink2); font-size: 15px; margin: 0 0 18px; }

/* ---------- 按钮 ---------- */
.q-actions { display: flex; gap: 10px; margin-top: 6px; }
.btn {
  flex: 1; padding: 13px 10px; font-size: 16px; font-weight: 700; border-radius: 13px;
  border: none; cursor: pointer; transition: transform .08s, filter .15s;
}
.btn:active { transform: scale(.97); }
.btn.primary { background: var(--pri); color: var(--pri-ink); box-shadow: 0 4px 16px rgba(37, 99, 235, .35); }
.btn.ghost { background: var(--ghost); color: var(--ghost-ink); }
.btn.big { font-size: 18px; padding: 15px 46px; flex: none; }

/* ---------- 答案区 ---------- */
.a-toolbar { display: flex; justify-content: space-between; gap: 8px; font-size: 12px; color: var(--ink2); margin-bottom: 8px; flex-wrap: wrap; }
.a-meta { word-break: break-all; }
.a-tip u { text-decoration-style: dashed; text-underline-offset: 3px; color: var(--term); }

/* ---------- Markdown 排版 ---------- */
.md { overflow-wrap: break-word; }
.md h2 { font-size: 18px; margin: 22px 0 8px; padding-left: 9px; border-left: 4px solid var(--pri); }
.md h3 { font-size: 16px; margin: 16px 0 6px; }
.md h4, .md h5 { font-size: 15px; margin: 12px 0 4px; }
.md p { margin: 8px 0; }
.md ul, .md ol { margin: 6px 0; padding-left: 22px; }
.md li { margin: 4px 0; }
.md blockquote { margin: 10px 0; padding: 6px 12px; border-left: 3px solid var(--pri); background: var(--ghost); border-radius: 0 10px 10px 0; color: var(--ink2); }
.md hr { border: none; border-top: 1px dashed var(--line); margin: 18px 0; }
.md pre {
  background: var(--code-bg); color: var(--code-ink); padding: 12px 14px; border-radius: 12px;
  overflow-x: auto; font-size: 12.5px; line-height: 1.5; margin: 10px 0;
  -webkit-overflow-scrolling: touch;
}
.md pre code { background: none; color: inherit; padding: 0; font-size: inherit; }
.md code {
  background: var(--ghost); color: var(--ghost-ink); padding: 1.5px 6px; border-radius: 6px;
  font-size: 13.5px; font-family: "JetBrains Mono", Consolas, Menlo, monospace;
}
.md .tbl { overflow-x: auto; -webkit-overflow-scrolling: touch; margin: 10px 0; }
.md table { border-collapse: collapse; font-size: 13.5px; min-width: 100%; }
.md th, .md td { border: 1px solid var(--line); padding: 7px 10px; text-align: left; white-space: nowrap; }
.md th { background: var(--ghost); }

/* ---------- 可点击术语 ---------- */
.term {
  color: var(--term); font-weight: 600; text-decoration: underline;
  text-decoration-style: dashed; text-decoration-color: var(--term);
  text-underline-offset: 3px; cursor: pointer; padding: 1px 0;
}
.term:active { background: var(--ghost); border-radius: 4px; }

/* ---------- 加载 ---------- */
#loadingCard { text-align: center; padding: 44px 18px; }
#loadingCard p { color: var(--ink2); font-size: 14.5px; }
.loader {
  width: 40px; height: 40px; margin: 0 auto 16px; border-radius: 50%;
  border: 4px solid var(--ghost); border-top-color: var(--pri);
  animation: spin .9s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }
.skeleton { margin-top: 22px; display: flex; flex-direction: column; gap: 10px; }
.skeleton i {
  height: 12px; border-radius: 6px; display: block;
  background: linear-gradient(90deg, var(--ghost) 25%, var(--line) 50%, var(--ghost) 75%);
  background-size: 200% 100%; animation: shimmer 1.3s infinite;
}
.skeleton i:nth-child(2) { width: 88%; }
.skeleton i:nth-child(3) { width: 74%; }
.skeleton i:nth-child(4) { width: 92%; }
@keyframes shimmer { from { background-position: 200% 0; } to { background-position: -200% 0; } }

/* ---------- 错误 ---------- */
#errorCard { text-align: center; }
.err-emoji { font-size: 40px; margin: 8px 0 4px; }
.err-msg { color: #dc2626; white-space: pre-wrap; margin-bottom: 18px; }
@media (prefers-color-scheme: dark) { .err-msg { color: #f87171; } }

/* ---------- 服务端地址设置 ---------- */
.srv-row { display: flex; gap: 8px; margin: 4px 0 14px; }
.srv-row input {
  flex: 1; min-width: 0; padding: 11px 12px; font-size: 14px; border-radius: 11px;
  border: 1px solid var(--line); background: var(--bg); color: var(--ink);
}
.srv-row .btn { flex: none; padding: 11px 14px; font-size: 14px; }

/* ---------- 术语详解底部弹层 ---------- */
.sheet-mask {
  position: fixed; inset: 0; background: rgba(2, 6, 23, .55); z-index: 40;
  animation: fade .2s ease;
}
@keyframes fade { from { opacity: 0; } }
.sheet {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 41;
  max-height: 72vh; overflow-y: auto; -webkit-overflow-scrolling: touch;
  background: var(--card); border-radius: 20px 20px 0 0; box-shadow: var(--sheet-shadow);
  padding: 8px 18px calc(16px + env(safe-area-inset-bottom));
  animation: slideup .25s ease;
}
@keyframes slideup { from { transform: translateY(40%); opacity: .4; } }
.sheet-grip { width: 44px; height: 5px; border-radius: 3px; background: var(--line); margin: 2px auto 8px; }
.sheet-head { display: flex; justify-content: space-between; align-items: center; }
.sheet-head h3 { margin: 4px 0; font-size: 18px; color: var(--term); }
.sheet-close { border: none; background: var(--ghost); color: var(--ink2); width: 32px; height: 32px; border-radius: 50%; font-size: 15px; cursor: pointer; }
.sheet-body { font-size: 14.5px; }
.sheet-search { display: flex; align-items: center; gap: 12px; font-size: 13px; color: var(--ink2); margin-top: 10px; padding-top: 10px; border-top: 1px dashed var(--line); }
.sheet-search a { color: var(--pri); font-weight: 600; text-decoration: none; }

/* ---------- 桌面端微调 ---------- */
@media (min-width: 640px) {
  body { font-size: 15.5px; }
  .wrap { padding-top: 24px; }
  .card { padding: 26px 30px; }
}

.foot { text-align: center; font-size: 12px; color: var(--ink2); margin-top: 26px; }