/* ToolNest — giao diện chung (sáng/tối theo máy người xem) */
:root {
  --bg: #f6f8fc; --bg-2: #eef2f9; --surface: #ffffff; --border: #e3e8f2; --text: #0f172a; --muted: #5b6577;
  --brand: #4f46e5; --brand-2: #7c3aed; --accent: #0ea5e9; --good: #059669; --bad: #dc2626; --warn: #d97706;
  --shadow: 0 1px 2px rgba(15, 23, 42, .04), 0 8px 24px rgba(15, 23, 42, .06);
  --radius: 14px;
}
@media (prefers-color-scheme: dark) {
  :root { --bg: #0b1020; --bg-2: #111832; --surface: #131b33; --border: #233056; --text: #e8edf9; --muted: #9aa6c1;
          --brand: #818cf8; --brand-2: #a78bfa; --accent: #38bdf8; --good: #34d399; --bad: #f87171; --warn: #fbbf24;
          --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 8px 24px rgba(0, 0, 0, .35); }
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--bg); color: var(--text); line-height: 1.6;
       font: 16px/1.6 Inter, ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }
img, svg { max-width: 100%; }
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 20px; }

/* Header */
.top { position: sticky; top: 0; z-index: 20; background: color-mix(in srgb, var(--bg) 82%, transparent);
       backdrop-filter: saturate(160%) blur(12px); border-bottom: 1px solid var(--border); }
.top .wrap { display: flex; align-items: center; gap: 18px; height: 62px; }
.logo { display: flex; align-items: center; gap: 9px; font-weight: 800; font-size: 19px; color: var(--text); letter-spacing: -.02em; }
.logo:hover { text-decoration: none; }
.logo i { width: 32px; height: 32px; border-radius: 10px; display: grid; place-items: center; font-style: normal;
          background: linear-gradient(135deg, var(--brand), var(--brand-2)); color: #fff; font-size: 17px; }
.nav { display: flex; gap: 4px; margin-left: auto; }
.nav a { color: var(--muted); padding: 7px 12px; border-radius: 9px; font-size: 14.5px; font-weight: 500; }
.nav a:hover { background: var(--bg-2); color: var(--text); text-decoration: none; }
@media (max-width: 720px) { .nav { display: none; } }

/* Hero */
.hero { padding: 64px 0 40px; text-align: center; position: relative; overflow: hidden; }
.hero::before { content: ""; position: absolute; inset: -40% 0 auto; height: 520px; z-index: -1;
                background: radial-gradient(closest-side, color-mix(in srgb, var(--brand) 22%, transparent), transparent),
                            radial-gradient(closest-side at 70% 40%, color-mix(in srgb, var(--accent) 18%, transparent), transparent); }
.hero h1 { font-size: clamp(32px, 5vw, 52px); line-height: 1.1; margin: 0 0 14px; letter-spacing: -.03em; }
.hero h1 span { background: linear-gradient(90deg, var(--brand), var(--brand-2), var(--accent));
                -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero p { color: var(--muted); font-size: 18px; max-width: 640px; margin: 0 auto 26px; }
@media (max-width: 720px) { .hero { padding-top: 40px; } .hero p { font-size: 16px; } }
.search { max-width: 560px; margin: 0 auto; position: relative; }
.search input { width: 100%; padding: 15px 18px 15px 46px; border-radius: 999px; border: 1px solid var(--border);
                background: var(--surface); color: var(--text); font-size: 16px; box-shadow: var(--shadow); outline: none; }
.search input:focus { border-color: var(--brand); }
.search::before { content: "🔍"; position: absolute; left: 18px; top: 50%; transform: translateY(-50%); font-size: 16px; }
.stats { display: flex; justify-content: center; gap: 28px; margin-top: 22px; color: var(--muted); font-size: 14px; flex-wrap: wrap; }
.stats b { color: var(--text); }

/* Danh mục + thẻ công cụ */
.cat { margin: 34px 0 10px; }
.cat h2 { font-size: 21px; margin: 0 0 14px; display: flex; align-items: center; gap: 10px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 14px; }
.card { display: flex; gap: 14px; padding: 18px; background: var(--surface); border: 1px solid var(--border);
        border-radius: var(--radius); color: var(--text); transition: transform .15s, border-color .15s, box-shadow .15s; }
.card:hover { transform: translateY(-2px); border-color: var(--brand); box-shadow: var(--shadow); text-decoration: none; }
.card .ic { flex: none; width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center; font-size: 22px;
            background: var(--bg-2); }
.card b { display: block; font-size: 15.5px; margin-bottom: 2px; }
.card small { color: var(--muted); font-size: 13.5px; line-height: 1.45; display: block; }

/* Trang công cụ */
.crumb { font-size: 13.5px; color: var(--muted); margin: 22px 0 8px; }
.crumb a { color: var(--muted); }
.tool-head h1 { font-size: clamp(28px, 4vw, 40px); margin: 0 0 8px; letter-spacing: -.02em; line-height: 1.15; }
.tool-head p { color: var(--muted); margin: 0 0 22px; font-size: 17px; max-width: 760px; }
.layout { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 24px; align-items: start; }
@media (max-width: 960px) { .layout { grid-template-columns: minmax(0, 1fr); } }
.panel { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow); }
.form { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 14px 16px; }
.field label { display: block; font-size: 13.5px; font-weight: 600; margin-bottom: 6px; color: var(--muted); }
.field input, .field select, .field textarea { width: 100%; padding: 11px 12px; border-radius: 10px; border: 1px solid var(--border);
       background: var(--bg); color: var(--text); font: inherit; font-size: 15.5px; outline: none; }
.field input:focus, .field select:focus, .field textarea:focus { border-color: var(--brand); box-shadow: 0 0 0 3px color-mix(in srgb, var(--brand) 18%, transparent); }
.field textarea { min-height: 180px; resize: vertical; }
.full { grid-column: 1 / -1; }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; padding: 11px 20px; border-radius: 10px;
       border: 0; cursor: pointer; font: inherit; font-weight: 600; color: #fff;
       background: linear-gradient(135deg, var(--brand), var(--brand-2)); }
.btn:hover { filter: brightness(1.07); }
.btn.ghost { background: var(--bg-2); color: var(--text); }
.seg { display: inline-flex; background: var(--bg-2); border-radius: 10px; padding: 3px; gap: 3px; }
.seg button { border: 0; background: none; color: var(--muted); padding: 7px 14px; border-radius: 8px; cursor: pointer; font: inherit; font-size: 14px; font-weight: 600; }
.seg button.on { background: var(--surface); color: var(--text); box-shadow: var(--shadow); }

.result { margin-top: 20px; padding: 20px; border-radius: 12px; background: linear-gradient(135deg,
          color-mix(in srgb, var(--brand) 9%, var(--surface)), color-mix(in srgb, var(--accent) 7%, var(--surface)));
          border: 1px solid color-mix(in srgb, var(--brand) 25%, var(--border)); }
.big { font-size: clamp(30px, 4vw, 40px); font-weight: 800; letter-spacing: -.02em; line-height: 1.15; }
.big small { font-size: 15px; font-weight: 600; color: var(--muted); letter-spacing: 0; }
.kpis { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 12px; margin-top: 14px; }
.kpi { background: var(--surface); border: 1px solid var(--border); border-radius: 10px; padding: 11px 13px; }
.kpi span { display: block; font-size: 12.5px; color: var(--muted); }
.kpi b { font-size: 18px; }
.bar { display: flex; height: 14px; border-radius: 99px; overflow: hidden; margin-top: 14px; background: var(--bg-2); }
.bar i { display: block; height: 100%; }
.scale { position: relative; margin-top: 30px; }
.scale .bar { margin-top: 0; }
.scale b { position: absolute; top: -24px; transform: translateX(-50%); font-size: 12px; background: var(--text); color: var(--bg); padding: 2px 7px; border-radius: 6px; white-space: nowrap; }
.scale b::after { content: ""; position: absolute; left: 50%; bottom: -4px; margin-left: -4px; border: 4px solid transparent; border-bottom: 0; border-top-color: var(--text); }
.scale .ticks { position: relative; height: 18px; font-size: 12px; color: var(--muted); }
.scale .ticks span { position: absolute; top: 4px; transform: translateX(-50%); }
.legend { display: flex; gap: 16px; flex-wrap: wrap; font-size: 13px; color: var(--muted); margin-top: 8px; }
.legend i { display: inline-block; width: 10px; height: 10px; border-radius: 3px; margin-right: 5px; vertical-align: -1px; }
.chart { display: flex; align-items: flex-end; gap: 3px; height: 170px; margin-top: 16px; border-bottom: 1px solid var(--border); }
.chart div { flex: 1; border-radius: 4px 4px 0 0; background: linear-gradient(180deg, var(--brand), var(--brand-2)); min-height: 2px; position: relative; }
.chart div i { position: absolute; bottom: 0; left: 0; right: 0; background: var(--accent); border-radius: 0 0 0 0; }
.table-wrap { overflow-x: auto; margin-top: 16px; max-height: 420px; overflow-y: auto; border: 1px solid var(--border); border-radius: 10px; }
table.t { width: 100%; border-collapse: collapse; font-size: 14px; }
table.t th, table.t td { padding: 8px 12px; text-align: right; border-bottom: 1px solid var(--border); white-space: nowrap; }
table.t th { position: sticky; top: 0; background: var(--bg-2); font-size: 12.5px; color: var(--muted); }
table.t th:first-child, table.t td:first-child { text-align: left; }
.note { font-size: 13px; color: var(--muted); margin-top: 10px; }
.good { color: var(--good); } .bad { color: var(--bad); }

/* Nội dung SEO */
.content { margin-top: 26px; }
.content h2 { font-size: 23px; margin: 30px 0 10px; letter-spacing: -.01em; }
.content h3 { font-size: 17px; margin: 18px 0 6px; }
.content p, .content li { color: color-mix(in srgb, var(--text) 86%, var(--muted)); }
.content code, .formula { font-family: ui-monospace, SFMono-Regular, Consolas, monospace; background: var(--bg-2);
                           padding: 2px 6px; border-radius: 6px; font-size: 14.5px; }
.formula { display: block; padding: 12px 14px; margin: 10px 0; overflow-x: auto; }
details.faq { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 4px 16px; margin: 10px 0; }
details.faq summary { cursor: pointer; font-weight: 600; padding: 10px 0; }
details.faq p { margin: 0 0 12px; }

/* Cột phải */
.side .panel { padding: 18px; position: sticky; top: 80px; }
.side h3 { margin: 0 0 10px; font-size: 15px; }
.side a { display: flex; gap: 10px; align-items: center; padding: 8px 6px; border-radius: 9px; color: var(--text); font-size: 14.5px; }
.side a:hover { background: var(--bg-2); text-decoration: none; }

/* Footer */
.foot { margin-top: 70px; border-top: 1px solid var(--border); padding: 34px 0 40px; color: var(--muted); font-size: 14px; }
.foot .cols { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 24px; }
@media (max-width: 720px) { .foot .cols { grid-template-columns: 1fr 1fr; } }
.foot h4 { color: var(--text); margin: 0 0 10px; font-size: 14.5px; }
.foot a { color: var(--muted); display: block; padding: 3px 0; }
.page { max-width: 820px; }
.page h1 { font-size: 36px; letter-spacing: -.02em; margin: 26px 0 10px; }
.hide { display: none !important; }