:root {
  --primary: #4f6ef7;
  --primary-dark: #3a55d4;
  --primary-light: #eef1fe;
  --success: #22c55e;
  --warning: #f59e0b;
  --danger: #ef4444;
  --text: #1f2937;
  --text-light: #6b7280;
  --bg: #f5f7fb;
  --card: #ffffff;
  --border: #e5e7eb;
  --radius: 12px;
  --shadow: 0 2px 12px rgba(31, 41, 55, 0.08);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-dark); }

/* ===== Navbar ===== */
.navbar {
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 100;
}
.nav-brand { display: flex; align-items: center; gap: 10px; font-size: 20px; font-weight: 700; color: var(--primary); cursor: pointer; }
.nav-brand .logo { width: 34px; height: 34px; border-radius: 8px; background: linear-gradient(135deg, var(--primary), #8b5cf6); display: flex; align-items: center; justify-content: center; color: #fff; font-size: 18px; font-weight: 800; }
.nav-links { display: flex; align-items: center; gap: 6px; }
.nav-link { padding: 8px 14px; border-radius: 8px; font-size: 14px; color: var(--text-light); cursor: pointer; border: none; background: none; }
.nav-link:hover { background: var(--primary-light); color: var(--primary); }
.nav-link.active { background: var(--primary-light); color: var(--primary); font-weight: 600; }
.nav-user { display: flex; align-items: center; gap: 10px; }
.user-badge { display: flex; align-items: center; gap: 8px; padding: 6px 12px; border-radius: 20px; background: var(--primary-light); font-size: 13px; font-weight: 600; color: var(--primary); cursor: pointer; }
.level-badge { font-size: 11px; padding: 2px 8px; border-radius: 10px; font-weight: 600; }
.level-normal { background: #e5e7eb; color: #4b5563; }
.level-level { background: #fef3c7; color: #b45309; }
.level-contest { background: #ede9fe; color: #6d28d9; }

/* ===== Layout ===== */
.container { max-width: 1200px; margin: 0 auto; padding: 24px 24px 60px; width: 100%; flex: 1; }
.page-title { font-size: 24px; font-weight: 700; margin-bottom: 6px; }
.page-sub { color: var(--text-light); font-size: 14px; margin-bottom: 24px; }

/* ===== Hero ===== */
.hero {
  background: linear-gradient(135deg, #4f6ef7 0%, #8b5cf6 100%);
  border-radius: 16px;
  padding: 40px 32px;
  color: #fff;
  margin-bottom: 28px;
}
.hero h1 { font-size: 28px; margin-bottom: 10px; }
.hero p { opacity: 0.9; font-size: 15px; margin-bottom: 20px; }
.hero-stats { display: flex; gap: 32px; flex-wrap: wrap; }
.hero-stat { text-align: center; }
.hero-stat .num { font-size: 28px; font-weight: 800; }
.hero-stat .label { font-size: 13px; opacity: 0.85; }

/* ===== Filter bar ===== */
.filter-bar { display: flex; gap: 10px; margin-bottom: 20px; flex-wrap: wrap; align-items: center; }
.chip { padding: 8px 16px; border-radius: 20px; border: 1px solid var(--border); background: var(--card); font-size: 14px; cursor: pointer; color: var(--text-light); transition: all .2s; }
.chip:hover { border-color: var(--primary); color: var(--primary); }
.chip.active { background: var(--primary); border-color: var(--primary); color: #fff; font-weight: 600; }

/* ===== Paper cards ===== */
.paper-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(340px, 1fr)); gap: 18px; }
.paper-card {
  background: var(--card);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  padding: 20px;
  cursor: pointer;
  transition: all .25s;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.paper-card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: var(--primary); }
.paper-card .top { display: flex; justify-content: space-between; align-items: flex-start; gap: 10px; }
.paper-card .title { font-size: 16px; font-weight: 700; line-height: 1.4; flex: 1; }
.paper-tag { font-size: 12px; padding: 3px 10px; border-radius: 6px; font-weight: 600; white-space: nowrap; }
.tag-mock { background: #dbeafe; color: #1d4ed8; }
.tag-real { background: #fce7f3; color: #be185d; }
.paper-card .desc { font-size: 13px; color: var(--text-light); line-height: 1.5; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; min-height: 38px; }
.paper-meta { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; background: var(--bg); border-radius: 10px; padding: 12px; }
.paper-meta .item { text-align: center; }
.paper-meta .val { font-size: 16px; font-weight: 700; color: var(--primary); }
.paper-meta .key { font-size: 11px; color: var(--text-light); margin-top: 2px; }
.paper-card .foot { display: flex; justify-content: space-between; align-items: center; font-size: 12px; color: var(--text-light); }
.level-chip { font-size: 11px; padding: 2px 8px; border-radius: 10px; background: #f3f4f6; color: #4b5563; }

/* ===== Buttons ===== */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 6px; padding: 10px 20px; border-radius: 10px; border: none; font-size: 14px; font-weight: 600; cursor: pointer; transition: all .2s; }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-outline { background: transparent; border: 1px solid var(--primary); color: var(--primary); }
.btn-outline:hover { background: var(--primary-light); }
.btn-ghost { background: transparent; color: var(--text-light); }
.btn-ghost:hover { background: var(--bg); }
.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover { opacity: 0.9; }
.btn-success { background: var(--success); color: #fff; }
.btn-sm { padding: 6px 12px; font-size: 13px; border-radius: 8px; }
.btn-lg { padding: 14px 28px; font-size: 16px; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

/* ===== Cards ===== */
.card { background: var(--card); border-radius: var(--radius); border: 1px solid var(--border); padding: 24px; margin-bottom: 18px; }
.card h3 { font-size: 17px; margin-bottom: 16px; }

/* ===== Forms ===== */
.form-group { margin-bottom: 16px; }
.form-group label { display: block; font-size: 13px; font-weight: 600; margin-bottom: 6px; color: var(--text); }
.form-control { width: 100%; padding: 10px 14px; border: 1px solid var(--border); border-radius: 10px; font-size: 14px; transition: border .2s; background: #fff; }
.form-control:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px rgba(79, 110, 247, 0.1); }
textarea.form-control { min-height: 90px; resize: vertical; }
select.form-control { appearance: auto; }
.form-hint { font-size: 12px; color: var(--text-light); margin-top: 4px; }

/* ===== Table ===== */
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 14px; }
th { text-align: left; padding: 12px 14px; background: var(--bg); color: var(--text-light); font-size: 12px; font-weight: 600; white-space: nowrap; }
td { padding: 12px 14px; border-bottom: 1px solid var(--border); vertical-align: middle; }
tr:hover td { background: #fafbfe; }

/* ===== Modal ===== */
.modal-mask { position: fixed; inset: 0; background: rgba(0,0,0,0.4); display: flex; align-items: center; justify-content: center; z-index: 200; }
.modal { background: #fff; border-radius: 16px; width: 90%; max-width: 620px; max-height: 85vh; overflow-y: auto; padding: 28px; }
.modal-title { font-size: 18px; font-weight: 700; margin-bottom: 20px; }
.modal-close { float: right; cursor: pointer; color: var(--text-light); font-size: 22px; line-height: 1; background: none; border: none; }

/* ===== Exam page ===== */
.exam-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 20px; }
.exam-timer { font-size: 20px; font-weight: 800; color: var(--danger); font-variant-numeric: tabular-nums; }
.exam-progress { font-size: 14px; color: var(--text-light); }
.question-block { background: var(--card); border-radius: var(--radius); border: 1px solid var(--border); padding: 28px; margin-bottom: 16px; }
.question-title { font-size: 16px; font-weight: 600; margin-bottom: 18px; line-height: 1.6; white-space: pre-wrap; word-break: break-word; }
.qtype-tag { font-size: 12px; padding: 2px 8px; border-radius: 6px; margin-right: 8px; font-weight: 600; }
.qt-single { background: #dbeafe; color: #1d4ed8; }
.qt-multi { background: #fef3c7; color: #b45309; }
.qt-judge { background: #d1fae5; color: #047857; }
.qt-fill { background: #ede9fe; color: #6d28d9; }
.option-list { display: flex; flex-direction: column; gap: 10px; }
.option-item { display: flex; align-items: center; gap: 12px; padding: 14px 16px; border: 1.5px solid var(--border); border-radius: 10px; cursor: pointer; transition: all .15s; font-size: 14px; }
.option-item:hover { border-color: var(--primary); background: var(--primary-light); }
.option-item.selected { border-color: var(--primary); background: var(--primary-light); font-weight: 600; }
.option-item .opt-radio { width: 20px; height: 20px; border-radius: 50%; border: 2px solid var(--border); flex-shrink: 0; display: flex; align-items: center; justify-content: center; font-size: 12px; color: #fff; }
.option-item.selected .opt-radio { background: var(--primary); border-color: var(--primary); }
.fill-input { width: 100%; min-height: 80px; padding: 12px 14px; border: 1.5px solid var(--border); border-radius: 10px; font-size: 14px; font-family: inherit; background: #fff; resize: vertical; }
.fill-input:focus { outline: none; border-color: var(--primary); }
.question-nav { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 20px; }
.qnav-item { width: 38px; height: 38px; border-radius: 8px; border: 1.5px solid var(--border); display: flex; align-items: center; justify-content: center; font-size: 13px; cursor: pointer; transition: all .15s; background: #fff; }
.qnav-item:hover { border-color: var(--primary); }
.qnav-item.answered { background: var(--success); border-color: var(--success); color: #fff; }
.qnav-item.marked { background: #f59e0b; border-color: #f59e0b; color: #fff; }
.qnav-item.answered.marked { background: linear-gradient(135deg, var(--success) 55%, #f59e0b 55%); border-color: var(--success); color: #fff; }
.qnav-item.current { border-color: var(--primary); box-shadow: 0 0 0 3px rgba(79,110,247,.15); font-weight: 700; }
.btn-warn { background: #f59e0b; color: #fff; border: 1px solid #f59e0b; }
.btn-warn:hover { background: #d97706; border-color: #d97706; }

/* ===== Result ===== */
.result-hero { text-align: center; padding: 40px; }
.result-score { font-size: 64px; font-weight: 800; color: var(--primary); }
.result-score.pass { color: var(--success); }
.result-score.fail { color: var(--danger); }
.result-stats { display: flex; justify-content: center; gap: 40px; margin: 24px 0; flex-wrap: wrap; }
.result-stat .val { font-size: 24px; font-weight: 700; }
.result-stat .key { font-size: 13px; color: var(--text-light); }
.review-block { background: var(--card); border-radius: var(--radius); border: 1px solid var(--border); padding: 22px; margin-bottom: 14px; }
.review-block .q { font-size: 15px; font-weight: 600; margin-bottom: 12px; white-space: pre-wrap; word-break: break-word; }
.review-answer { display: flex; gap: 24px; font-size: 14px; margin-bottom: 10px; flex-wrap: wrap; }
.ans-correct { color: var(--success); font-weight: 600; }
.ans-wrong { color: var(--danger); font-weight: 600; }
.review-analysis { background: var(--primary-light); border-radius: 8px; padding: 12px 14px; font-size: 13px; color: #4b5563; line-height: 1.6; }

/* ===== Admin ===== */
.admin-layout { display: flex; gap: 24px; }
.admin-side { width: 200px; flex-shrink: 0; }
.admin-side .nav-link { display: block; width: 100%; text-align: left; margin-bottom: 4px; }
.admin-main { flex: 1; min-width: 0; }
.sub-tabs { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 16px; border-bottom: 1px solid var(--border); padding-bottom: 10px; }
.sub-tab { padding: 8px 16px; border-radius: 8px; font-size: 14px; color: var(--text-light); cursor: pointer; border: 1px solid var(--border); background: var(--card); }
.sub-tab:hover { background: var(--primary-light); color: var(--primary); }
.sub-tab.active { background: var(--primary); color: #fff; border-color: var(--primary); font-weight: 600; }
.stat-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 16px; margin-bottom: 24px; }
.stat-card { background: var(--card); border-radius: var(--radius); border: 1px solid var(--border); padding: 20px; }
.stat-card .val { font-size: 28px; font-weight: 800; color: var(--primary); }
.stat-card .key { font-size: 13px; color: var(--text-light); margin-top: 4px; }

/* ===== Auth ===== */
.auth-wrap { display: flex; align-items: center; justify-content: center; min-height: calc(100vh - 60px); padding: 40px 20px; }
.auth-card { background: var(--card); border-radius: 16px; border: 1px solid var(--border); width: 100%; max-width: 400px; padding: 36px; box-shadow: var(--shadow); }
.auth-card h2 { font-size: 22px; margin-bottom: 6px; text-align: center; }
.auth-card .sub { text-align: center; color: var(--text-light); font-size: 13px; margin-bottom: 28px; }
.auth-footer { text-align: center; font-size: 13px; color: var(--text-light); margin-top: 20px; }

/* ===== Footer ===== */
.footer { text-align: center; padding: 20px; color: var(--text-light); font-size: 13px; border-top: 1px solid var(--border); background: var(--card); }

/* ===== Toast ===== */
.toast { position: fixed; top: 80px; left: 50%; transform: translateX(-50%); background: #1f2937; color: #fff; padding: 12px 24px; border-radius: 10px; font-size: 14px; z-index: 999; box-shadow: 0 8px 24px rgba(0,0,0,.2); opacity: 0; transition: all .3s; pointer-events: none; }
.toast.show { opacity: 1; }
.toast.error { background: var(--danger); }
.toast.success { background: var(--success); }

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .container { padding: 16px; }
  .hero { padding: 24px 20px; }
  .hero h1 { font-size: 22px; }
  .paper-grid { grid-template-columns: 1fr; }
  .admin-layout { flex-direction: column; }
  .admin-side { width: 100%; display: flex; gap: 6px; overflow-x: auto; }
  .admin-side .nav-link { width: auto; white-space: nowrap; }
  .nav-links { gap: 2px; }
  .nav-link { padding: 8px 10px; font-size: 13px; }
  .paper-meta { grid-template-columns: repeat(4, 1fr); }
}

/* ===== Panel & Table ===== */
.panel { background: var(--card); border-radius: var(--radius); border: 1px solid var(--border); padding: 20px; margin-bottom: 20px; }
.data-table { width: 100%; border-collapse: collapse; font-size: 14px; }
.data-table th { text-align: left; padding: 12px 14px; background: var(--bg); color: var(--text-light); font-size: 12px; font-weight: 600; white-space: nowrap; }
.data-table td { padding: 12px 14px; border-bottom: 1px solid var(--border); vertical-align: middle; }
.data-table tr:hover td { background: #fafbfe; }
.pager { display: flex; gap: 8px; margin-top: 16px; flex-wrap: wrap; }

/* ===== Status badge ===== */
.status-badge { display: inline-block; padding: 3px 10px; border-radius: 8px; font-size: 12px; font-weight: 700; }
.st-ac { background: #d1fae5; color: #047857; }
.st-wa { background: #fee2e2; color: #b91c1c; }
.st-tle { background: #fef3c7; color: #b45309; }
.st-ce { background: #ede9fe; color: #6d28d9; }
.st-re { background: #fce7f3; color: #be185d; }
.st-draft { background: #e2e8f0; color: #475569; }

/* ===== Hero sm ===== */
.hero-sm { padding: 24px 28px; margin-bottom: 22px; }
.hero-sm h1 { font-size: 22px; }
.hero-sm p { font-size: 14px; margin-bottom: 0; }

/* ===== OJ ===== */
.oj-layout { display: flex; gap: 20px; align-items: flex-start; }
.oj-head { margin-bottom: 16px; }
.oj-meta { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 10px; }
.oj-desc { font-size: 14px; line-height: 1.8; color: var(--text); }
.oj-desc h4 { margin: 16px 0 6px; font-size: 15px; }
.oj-samples { margin-top: 18px; }
.sample-box { margin-bottom: 12px; }
.sample-title { font-size: 12px; font-weight: 700; color: var(--text-light); margin-bottom: 6px; }
.sample-box pre { background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 12px 14px; font-size: 13px; overflow-x: auto; font-family: "SF Mono", Consolas, monospace; }
.hint-box { background: #fffbeb; border: 1px solid #fde68a; border-radius: 8px; padding: 12px 14px; font-size: 13px; color: #92400e; line-height: 1.6; }
.oj-editor-head { display: flex; gap: 10px; align-items: center; margin-bottom: 12px; flex-wrap: wrap; }
.code-area { width: 100%; min-height: 420px; border: 1px solid var(--border); border-radius: 10px; padding: 14px; font-family: "SF Mono", Consolas, "Courier New", monospace; font-size: 13.5px; line-height: 1.6; resize: vertical; background: #0f172a; color: #e2e8f0; tab-size: 2; }
.code-area:focus { outline: none; border-color: var(--primary); }
.code-pre { background: #0f172a; color: #e2e8f0; border-radius: 8px; padding: 12px 14px; font-size: 13px; overflow-x: auto; font-family: "SF Mono", Consolas, monospace; line-height: 1.5; white-space: pre-wrap; word-break: break-all; }
.judge-box { background: var(--bg); border: 1px solid var(--border); border-radius: 10px; padding: 16px; }
.modal-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: 16px; }
.modal-body h4 { font-size: 14px; margin: 14px 0 6px; }

@media (max-width: 768px) {
  .oj-layout { flex-direction: column; }
  .code-area { min-height: 300px; }
}