/*
 * base.css — Màu sắc (sáng/tối), nền tảng, thanh trên cùng, nút, nhãn, thẻ, hộp thoại, toast.
 */
:root {
  --bg: #f5f7fb;
  --surface: #ffffff;
  --surface-2: #f1f4f9;
  --surface-3: #e7ecf4;
  --border: #e1e6ef;
  --text: #1b2333;
  --muted: #66728a;
  --primary: #2f6fb0;
  --primary-hover: #255b93;
  --primary-soft: #e3eefa;
  --on-primary: #ffffff;
  --accent: #ffd43b;
  --accent-soft: #fff6d1;
  --good: #15803d;
  --good-soft: #dcfce7;
  --bad: #c62828;
  --bad-soft: #fde6e6;
  --warn: #b45309;
  --warn-soft: #fef3c7;
  --easy: #0f9d84;
  --medium: #c98200;
  --hard: #e0354f;
  --code-bg: #f6f8fb;
  --tok-kw: #7c3aed;
  --tok-def: #0b62c4;
  --tok-builtin: #0f766e;
  --tok-string: #b45309;
  --tok-number: #c2410c;
  --tok-comment: #7b8496;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.06), 0 4px 14px rgba(16, 24, 40, 0.05);
  --radius: 12px;
  --header-h: 56px;
  --font: "Segoe UI", system-ui, -apple-system, Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: "Cascadia Code", "JetBrains Mono", Consolas, "SF Mono", Menlo, monospace;
  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #0e131d;
  --surface: #161d2a;
  --surface-2: #1b2331;
  --surface-3: #243042;
  --border: #2a3446;
  --text: #e5e9f2;
  --muted: #95a1b8;
  --primary: #5b9ee0;
  --primary-hover: #7ab2ea;
  --primary-soft: #1c3350;
  --on-primary: #0b1220;
  --accent-soft: #3a3215;
  --good: #4ade80;
  --good-soft: #13321f;
  --bad: #f87171;
  --bad-soft: #3b1d20;
  --warn: #fbbf24;
  --warn-soft: #3a2e10;
  --easy: #2dd4bf;
  --medium: #fbbf24;
  --hard: #fb7185;
  --code-bg: #111824;
  --tok-kw: #c792ea;
  --tok-def: #82aaff;
  --tok-builtin: #89ddff;
  --tok-string: #c3e88d;
  --tok-number: #f78c6c;
  --tok-comment: #6f7d95;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 4px 14px rgba(0, 0, 0, 0.25);
  color-scheme: dark;
}

* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.55;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3, h4 { line-height: 1.25; margin: 0 0 0.5em; }
h1 { font-size: 1.6rem; }
h2 { font-size: 1.15rem; }
code, pre, kbd, textarea.stdin-box, .predict-input { font-family: var(--mono); }
code { background: var(--surface-3); padding: 0.1em 0.35em; border-radius: 5px; font-size: 0.9em; }
pre code { background: none; padding: 0; }
small { font-size: 0.82em; }
.muted { color: var(--muted); }
.spacer { flex: 1; }
.grow { flex: 1; min-width: 0; }
[hidden] { display: none !important; }
:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }

/* ----- Thanh trên cùng ----- */
.app-header {
  position: sticky; top: 0; z-index: 20;
  height: var(--header-h);
  display: flex; align-items: center; gap: 16px;
  padding: 0 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.brand { font-size: 1.05rem; font-weight: 800; letter-spacing: -0.01em; color: var(--text); white-space: nowrap; }
.brand:hover { text-decoration: none; }
.main-nav { display: flex; gap: 2px; }
.nav-link {
  display: flex; align-items: center; gap: 6px;
  padding: 6px 12px; border-radius: 8px;
  color: var(--muted); font-weight: 600;
}
.nav-link:hover { background: var(--surface-2); text-decoration: none; color: var(--text); }
.nav-link.active { color: var(--text); background: var(--surface-2); }
.header-right { margin-left: auto; display: flex; align-items: center; gap: 14px; }
.py-status { display: inline-flex; align-items: center; gap: 6px; font-size: 0.8rem; color: var(--muted); }
.status-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--muted); flex: none; }
.status-ready { background: var(--good); }
.status-loading, .status-busy { background: var(--medium); animation: pulse 1.2s ease-in-out infinite; }
.status-error { background: var(--bad); }
@keyframes pulse { 50% { opacity: 0.35; } }
.stat { font-size: 0.85rem; color: var(--muted); white-space: nowrap; }
.stat b { color: var(--text); font-size: 0.95rem; }
.stat.dim b { color: var(--muted); }
.icon { display: inline-block; vertical-align: -3px; flex: none; }
.badge {
  display: inline-grid; place-items: center; min-width: 20px; height: 20px; padding: 0 6px;
  border-radius: 999px; background: var(--hard); color: #fff; font-size: 0.72rem; font-weight: 700;
}
.profile-chip {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 3px 12px 3px 3px; border-radius: 999px; border: 1px solid var(--border);
  color: var(--text); font-weight: 600;
}
.profile-chip:hover { text-decoration: none; background: var(--surface-2); }

/* Hình đại diện: chữ cái đầu trên nền màu */
.avatar {
  display: inline-grid; place-items: center; flex: none;
  width: 28px; height: 28px; border-radius: 50%;
  font-size: 0.85rem; font-weight: 700; color: #fff; background: var(--muted);
}
.avatar-sm { width: 20px; height: 20px; font-size: 0.7rem; }
.avatar-lg { width: 52px; height: 52px; font-size: 1.4rem; }
.av-blue { background: #2f6fb0; }
.av-green { background: #2e8b57; }
.av-orange { background: #d9772b; }
.av-pink { background: #c2477e; }
.av-purple { background: #7a4fc4; }
.av-teal { background: #138a8a; }
.av-red { background: #c94040; }
.av-slate { background: #5b6b82; }
.av-add { background: transparent; color: var(--muted); border: 2px dashed var(--border); }

/* Chấm trạng thái bài: xong / đang làm / chưa làm / sai */
.st { display: inline-block; width: 12px; height: 12px; border-radius: 50%; flex: none; vertical-align: -1px; }
.st-solved { background: var(--good); }
.st-tried { background: var(--medium); }
.st-new { border: 2px solid var(--surface-3); }
.st-fail { background: var(--bad); }

/* Số thứ tự unit */
.unit-num {
  display: inline-grid; place-items: center; flex: none;
  width: 30px; height: 30px; border-radius: 8px;
  background: var(--surface-2); color: var(--muted); font-weight: 700; font-size: 0.9rem;
}
.good { color: var(--good); }
.bad { color: var(--bad); }
.eyebrow { margin: 0 0 2px; font-size: 0.75rem; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); }
.count {
  display: inline-grid; place-items: center; min-width: 22px; height: 22px; padding: 0 7px; margin-left: 6px;
  border-radius: 999px; background: var(--surface-2); color: var(--muted); font-size: 0.8rem; vertical-align: 2px;
}

/* ----- Nút ----- */
.btn, .icon-btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  font: inherit; font-weight: 600; cursor: pointer;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  border-radius: 10px; padding: 8px 14px; white-space: nowrap;
  transition: background 0.15s, border-color 0.15s, transform 0.05s;
}
.btn:hover, .icon-btn:hover { background: var(--surface-2); text-decoration: none; }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: 0.55; cursor: progress; }
.btn-primary { background: var(--primary); border-color: var(--primary); color: var(--on-primary); }
.btn-primary:hover { background: var(--primary-hover); border-color: var(--primary-hover); }
.btn-danger { background: var(--bad); border-color: var(--bad); color: #fff; }
.btn-danger-soft { color: var(--bad); }
.btn-review { background: var(--accent-soft); border-color: var(--accent); }
.btn-ghost { border-color: transparent; background: transparent; }
.btn-sm { padding: 4px 10px; font-size: 0.85rem; }
.btn-lg { padding: 11px 20px; font-size: 1.02rem; }
.icon-btn { padding: 5px 9px; border-radius: 8px; font-size: 0.9rem; }
.icon-btn.disabled { opacity: 0.35; pointer-events: none; }

/* ----- Nhãn / thẻ ----- */
.chip {
  font: inherit; font-size: 0.85rem; font-weight: 600; cursor: pointer;
  padding: 5px 12px; border-radius: 999px; border: 1px solid var(--border);
  background: var(--surface); color: var(--muted); white-space: nowrap;
}
.chip:hover { color: var(--text); text-decoration: none; }
.chip.active { background: var(--primary-soft); border-color: var(--primary); color: var(--primary); }
.chip-person { display: inline-flex; align-items: center; gap: 6px; padding-left: 5px; }
.tag {
  display: inline-flex; align-items: center; gap: 4px;
  padding: 2px 9px; border-radius: 999px; background: var(--surface-2);
  font-size: 0.78rem; font-weight: 600; color: var(--muted); white-space: nowrap;
}
.tag-review { background: var(--accent-soft); color: var(--warn); }
.lvl { font-weight: 700; font-size: 0.82rem; white-space: nowrap; }
.lvl-easy { color: var(--easy); }
.lvl-medium { color: var(--medium); }
.lvl-hard { color: var(--hard); }
.p-tags .lvl { padding: 2px 9px; border-radius: 999px; background: var(--surface-2); }

.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow); padding: 18px 20px;
}
.progress { display: block; height: 6px; border-radius: 999px; background: var(--surface-3); overflow: hidden; }
.progress > span { display: block; height: 100%; border-radius: inherit; background: linear-gradient(90deg, var(--easy), var(--primary)); }
.progress.big { height: 10px; margin-top: 10px; }
.empty { text-align: center; color: var(--muted); padding: 28px 12px; }
.note { font-size: 0.88rem; color: var(--muted); background: var(--surface-2); padding: 8px 12px; border-radius: 8px; }

/* ----- Markdown & code tô màu ----- */
.md p { margin: 0 0 0.7em; }
.md ul, .md ol { margin: 0 0 0.7em; padding-left: 1.4em; }
.md pre, .code-block, pre.io {
  background: var(--code-bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px 12px; overflow-x: auto; font-size: 0.88rem; line-height: 1.5; margin: 0 0 0.8em;
}
.md blockquote {
  margin: 0 0 0.8em; padding: 8px 12px; border-left: 4px solid var(--primary);
  background: var(--primary-soft); border-radius: 0 8px 8px 0;
}
.md blockquote p:last-child { margin: 0; }
.md table { border-collapse: collapse; margin-bottom: 0.8em; }
.md th, .md td { border: 1px solid var(--border); padding: 4px 10px; }
.code-block .cm-keyword { color: var(--tok-kw); font-weight: 600; }
.code-block .cm-def { color: var(--tok-def); }
.code-block .cm-builtin { color: var(--tok-builtin); }
.code-block .cm-string { color: var(--tok-string); }
.code-block .cm-number { color: var(--tok-number); }
.code-block .cm-comment { color: var(--tok-comment); font-style: italic; }
.code-block .cm-variable-2, .code-block .cm-property { color: var(--tok-def); }

/* ----- Hộp thoại & toast ----- */
.modal-backdrop {
  position: fixed; inset: 0; z-index: 50; display: grid; place-items: center; padding: 16px;
  background: rgba(10, 14, 22, 0.55);
}
.modal { width: min(440px, 100%); background: var(--surface); border-radius: 16px; padding: 22px; box-shadow: var(--shadow); }
.modal-body { color: var(--muted); margin-bottom: 18px; }
.modal-actions { display: flex; justify-content: flex-end; gap: 8px; }
.toast-host { position: fixed; z-index: 60; right: 16px; bottom: 16px; display: grid; gap: 8px; }
.toast {
  padding: 11px 16px; border-radius: 12px; background: var(--surface); border: 1px solid var(--border);
  box-shadow: var(--shadow); font-weight: 600; transform: translateY(10px); opacity: 0; transition: 0.25s;
}
.toast.show { transform: none; opacity: 1; }
.toast-success { border-color: var(--good); background: var(--good-soft); }
.toast-error { border-color: var(--bad); background: var(--bad-soft); }

.app-view { padding: 20px 24px 40px; max-width: 1280px; margin: 0 auto; }
.app-view.view-problem { padding: 0; max-width: none; }

@media (max-width: 900px) {
  .py-status-text, .profile-name { display: none; }
  .app-header { gap: 8px; padding: 0 10px; }
  .header-right { gap: 10px; }
  .nav-link { padding: 6px 8px; }
  .profile-chip { padding: 2px; }
  .app-view { padding: 14px 16px 32px; }
}
@media (max-width: 520px) {
  .brand, .stat-streak { display: none; }
  .main-nav { gap: 0; }
  .nav-link { padding: 6px 7px; font-size: 0.9rem; }
}