/* MolBay — clean light design system (devbay family, teal accent) */
:root {
    --bg: #f8fafc;
    --bg-soft: #f1f5f9;
    --text: #0f172a;
    --text-dim: #64748b;
    --text-faint: #94a3b8;
    --card: #ffffff;
    --card-strong: #f8fafc;
    --border: #e2e8f0;
    --border-strong: #cbd5e1;
    --accent-1: #0d9488;
    --accent-2: #0f766e;
    --accent-3: #14b8a6;
    --accent-soft: rgba(13, 148, 136, 0.08);
    --good: #10b981;
    --good-soft: rgba(16, 185, 129, 0.1);
    --warn: #d97706;
    --warn-soft: rgba(245, 158, 11, 0.12);
    --danger: #dc2626;
    --danger-soft: rgba(220, 38, 38, 0.08);
    --radius: 0.625rem;
    --shadow: 0 1px 2px 0 rgba(15, 23, 42, 0.04);
    --shadow-hover: 0 4px 12px 0 rgba(15, 23, 42, 0.08);
    --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC",
            "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", "Apple SD Gothic Neo",
            "Malgun Gothic", sans-serif;

    /* periodic table: family colors (light) */
    --pt-alkali-bg: #ffe4e6;   --pt-alkali-bd: #fecdd3;   --pt-alkali-tx: #9f1239;
    --pt-alkaline-bg: #ffedd5; --pt-alkaline-bd: #fed7aa; --pt-alkaline-tx: #9a3412;
    --pt-transition-bg: #e0f2fe; --pt-transition-bd: #bae6fd; --pt-transition-tx: #075985;
    --pt-post-bg: #fef9c3;     --pt-post-bd: #fef08a;     --pt-post-tx: #854d0e;
    --pt-metalloid-bg: #dcfce7; --pt-metalloid-bd: #bbf7d0; --pt-metalloid-tx: #166534;
    --pt-nonmetal-bg: #ccfbf1; --pt-nonmetal-bd: #99f6e4; --pt-nonmetal-tx: #115e59;
    --pt-noble-bg: #ede9fe;    --pt-noble-bd: #ddd6fe;    --pt-noble-tx: #5b21b6;
    --pt-lanthanide-bg: #fce7f3; --pt-lanthanide-bd: #fbcfe8; --pt-lanthanide-tx: #9d174d;
    --pt-actinide-bg: #e0e7ff; --pt-actinide-bd: #c7d2fe; --pt-actinide-tx: #3730a3;
    --pt-unknown-bg: #f1f5f9;  --pt-unknown-bd: #e2e8f0;  --pt-unknown-tx: #475569;
}

[data-theme="dark"] {
    --bg: #0f172a;
    --bg-soft: #1e293b;
    --text: #f1f5f9;
    --text-dim: #94a3b8;
    --text-faint: #64748b;
    --card: #1e293b;
    --card-strong: #0f172a;
    --border: #334155;
    --border-strong: #475569;
    --accent-1: #2dd4bf;
    --accent-2: #0d9488;
    --accent-3: #14b8a6;
    --accent-soft: rgba(45, 212, 191, 0.13);
    --good: #34d399;
    --good-soft: rgba(52, 211, 153, 0.12);
    --warn: #fbbf24;
    --warn-soft: rgba(251, 191, 36, 0.12);
    --danger: #f87171;
    --danger-soft: rgba(248, 113, 113, 0.1);
    --shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 4px 12px 0 rgba(0, 0, 0, 0.4);

    --pt-alkali-bg: #431d24;   --pt-alkali-bd: #9f3c4c;   --pt-alkali-tx: #fecdd3;
    --pt-alkaline-bg: #4a2b17; --pt-alkaline-bd: #9a5b25; --pt-alkaline-tx: #fed7aa;
    --pt-transition-bg: #0c3350; --pt-transition-bd: #155e8f; --pt-transition-tx: #bae6fd;
    --pt-post-bg: #4a3f14;     --pt-post-bd: #8a7a23;     --pt-post-tx: #fde68a;
    --pt-metalloid-bg: #143c24; --pt-metalloid-bd: #2f6e43; --pt-metalloid-tx: #bbf7d0;
    --pt-nonmetal-bg: #0f3d35; --pt-nonmetal-bd: #1f6f62; --pt-nonmetal-tx: #99f6e4;
    --pt-noble-bg: #2e2449;    --pt-noble-bd: #5b4a8c;    --pt-noble-tx: #ddd6fe;
    --pt-lanthanide-bg: #47233a; --pt-lanthanide-bd: #8c3a6f; --pt-lanthanide-tx: #fbcfe8;
    --pt-actinide-bg: #202a55; --pt-actinide-bd: #3e51a8; --pt-actinide-tx: #c7d2fe;
    --pt-unknown-bg: #27272a;  --pt-unknown-bd: #3f3f46;  --pt-unknown-tx: #d4d4d8;
}

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

html { scroll-behavior: smooth; }

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
    transition: background 0.3s ease, color 0.3s ease;
}

.container { width: min(1160px, 94vw); margin: 0 auto; }
.container-wide { width: min(1240px, 96vw); margin: 0 auto; }

/* ---------- header ---------- */
.site-header {
    position: sticky; top: 0; z-index: 50;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
}
.nav { display: flex; align-items: center; justify-content: space-between; height: 64px; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text); }
.brand-logo { display: flex; }
.brand-name { font-size: 1.25rem; font-weight: 800; letter-spacing: -0.02em; }
.brand-accent { color: var(--accent-1); }
.nav-links { display: flex; align-items: center; gap: 4px; }
.nav-link {
    padding: 6px 12px; border-radius: 0.5rem;
    color: var(--text-dim); text-decoration: none;
    font-size: 0.9rem; font-weight: 600; transition: all 0.15s ease;
    white-space: nowrap;
}
.nav-link:hover { color: var(--text); background: var(--bg-soft); }
.nav-link.active { color: var(--accent-1); background: var(--accent-soft); }
.nav-right { display: flex; align-items: center; gap: 10px; }
.icon-btn {
    display: flex; align-items: center; justify-content: center;
    width: 38px; height: 38px; border-radius: 0.5rem;
    background: var(--card); border: 1px solid var(--border);
    color: var(--text-dim); cursor: pointer; transition: all 0.15s ease;
    font-family: inherit;
}
.icon-btn:hover { color: var(--text); border-color: var(--border-strong); background: var(--card-strong); }
.icon-moon { display: none; }
[data-theme="light"] .icon-sun { display: none; }
[data-theme="light"] .icon-moon { display: block; }

.lang-select {
    appearance: none; -webkit-appearance: none;
    background: var(--card); border: 1px solid var(--border);
    border-radius: 0.5rem; color: var(--text-dim);
    font-family: inherit; font-size: 0.8rem; font-weight: 600;
    padding: 8px 28px 8px 12px; cursor: pointer; transition: all 0.15s ease;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6' viewBox='0 0 10 6'%3E%3Cpath d='M1 1l4 4 4-4' stroke='%2394a3b8' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
    background-repeat: no-repeat; background-position: right 10px center;
}
.lang-select:hover { color: var(--text); border-color: var(--border-strong); }

/* ---------- page head ---------- */
.page-head { padding: 40px 0 6px; }
.page-head h1 { font-size: clamp(1.6rem, 4vw, 2.2rem); font-weight: 800; letter-spacing: -0.02em; }
.page-sub { color: var(--text-dim); margin-top: 6px; max-width: 760px; }
.breadcrumb-line { margin-top: 10px; }

/* ---------- cards & forms ---------- */
.card {
    background: var(--card); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 24px;
    box-shadow: var(--shadow); margin-bottom: 20px;
}
.card-title { font-size: 1.1rem; font-weight: 800; margin-bottom: 14px; }
.card-title small { font-weight: 600; color: var(--text-faint); font-size: 0.8rem; }
.form-row {
    display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px; margin-bottom: 16px; align-items: end;
}
.form-row:last-child { margin-bottom: 0; }
.field { display: flex; flex-direction: column; gap: 6px; }
.field-label { font-size: 0.8rem; font-weight: 600; color: var(--text-dim); }
.field-hint { font-size: 0.75rem; color: var(--text-faint); }

.input {
    width: 100%;
    background: var(--card); border: 1px solid var(--border);
    border-radius: 0.5rem; padding: 9px 12px;
    font-family: inherit; font-size: 0.95rem; color: var(--text);
    transition: border-color 0.15s ease, box-shadow 0.15s ease;
}
.input:focus { outline: none; border-color: var(--accent-1); box-shadow: 0 0 0 3px var(--accent-soft); }
select.input { cursor: pointer; }
.input-mono { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 1rem; }
.input-invalid { border-color: var(--danger); }
.input-invalid:focus { box-shadow: 0 0 0 3px var(--danger-soft); }

.seg { display: inline-flex; background: var(--bg-soft); border: 1px solid var(--border); border-radius: 0.5rem; padding: 3px; gap: 3px; flex-wrap: wrap; }
.seg-btn {
    border: none; background: transparent; border-radius: 0.375rem;
    padding: 7px 14px; font-family: inherit; font-size: 0.9rem; font-weight: 600;
    color: var(--text-dim); cursor: pointer; transition: all 0.15s ease;
}
.seg-btn:hover { color: var(--text); }
.seg-btn.active { background: var(--card); color: var(--accent-1); box-shadow: var(--shadow); }

.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
    border: 1px solid var(--border); background: var(--card);
    border-radius: 999px; padding: 6px 14px;
    font-family: inherit; font-size: 0.85rem; font-weight: 600; color: var(--text-dim);
    cursor: pointer; transition: all 0.15s ease;
}
.chip:hover { color: var(--accent-1); border-color: var(--accent-3); }

/* ---------- buttons ---------- */
.btn {
    border: 1px solid var(--border); background: var(--card);
    border-radius: 0.5rem; padding: 9px 18px;
    font-family: inherit; font-size: 0.9rem; font-weight: 600;
    color: var(--text-dim); cursor: pointer; transition: all 0.15s ease;
}
.btn:hover { color: var(--text); border-color: var(--border-strong); background: var(--card-strong); }
.btn-primary { background: var(--accent-2); border-color: var(--accent-2); color: #fff; }
.btn-primary:hover { background: var(--accent-1); border-color: var(--accent-1); color: #fff; }
.btn-sm { padding: 5px 12px; font-size: 0.8rem; border-radius: 0.375rem; }
.form-actions { display: flex; gap: 10px; margin-top: 4px; align-items: center; flex-wrap: wrap; }

/* ---------- results ---------- */
.result-area { margin-top: 20px; border-top: 1px solid var(--border); padding-top: 20px; }
.result-card {
    display: flex; align-items: baseline; gap: 8px; flex-wrap: wrap;
    background: var(--card-strong); border: 1px solid var(--border);
    border-radius: var(--radius); padding: 18px 20px;
}
.result-num { font-size: 2rem; font-weight: 900; letter-spacing: -0.03em; color: var(--accent-1); word-break: break-word; }
.result-unit { font-size: 1rem; font-weight: 600; color: var(--text-dim); }
.result-label { width: 100%; font-size: 0.8rem; font-weight: 600; color: var(--text-faint); text-transform: uppercase; letter-spacing: 0.05em; }
.result-side { display: flex; flex-direction: column; gap: 6px; margin-left: auto; text-align: right; }
.stage-desc { font-size: 0.85rem; color: var(--text-dim); }
.result-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(170px, 1fr)); gap: 12px; }
.result-card-accent { background: var(--accent-soft); border-color: var(--accent-3); }
.result-card-accent .result-num { color: var(--accent-2); }
.formula-line { font-size: 1.1rem; font-weight: 600; color: var(--text-dim); margin-bottom: 4px; }
.formula-line sub { font-size: 0.7em; }

.note { font-size: 0.8rem; color: var(--text-faint); margin-top: 14px; line-height: 1.7; }
.muted { color: var(--text-dim); font-size: 0.9rem; }

/* ---------- notices ---------- */
.notice {
    border-radius: var(--radius); padding: 12px 16px; font-size: 0.9rem; font-weight: 600;
    margin-bottom: 14px;
}
.notice-warn { background: var(--warn-soft); color: var(--warn); }
.notice-error { background: var(--danger-soft); color: var(--danger); }

/* ---------- periodic table ---------- */
.pt-controls { display: flex; align-items: center; justify-content: space-between; gap: 14px; flex-wrap: wrap; margin-bottom: 14px; }
.pt-search { position: relative; flex: 1; min-width: 220px; max-width: 360px; }
.pt-search .input { padding-left: 34px; }
.pt-search-icon {
    position: absolute; left: 11px; top: 50%; transform: translateY(-50%);
    color: var(--text-faint); pointer-events: none; display: flex;
}
.pt-count { font-size: 0.8rem; color: var(--text-faint); font-weight: 600; white-space: nowrap; }
.pt-wrap { overflow-x: auto; padding-bottom: 6px; }
.pt-grid {
    display: grid;
    grid-template-columns: repeat(18, minmax(38px, 1fr));
    grid-auto-rows: var(--cell-h, 50px);
    gap: 4px;
    width: 100%;
    min-width: 752px;
}
.pt-cell {
    position: relative;
    border-radius: 6px;
    border: 1px solid var(--border);
    background: var(--card);
    cursor: pointer;
    display: flex; flex-direction: column; align-items: center; justify-content: center;
    font-family: inherit;
    transition: transform 0.12s ease, box-shadow 0.12s ease, border-color 0.12s ease, opacity 0.2s ease;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
}
.pt-cell:hover { transform: translateY(-1px); box-shadow: var(--shadow-hover); z-index: 2; border-color: var(--border-strong); }
.pt-cell .pt-num {
    position: absolute; top: 3px; left: 6px;
    font-size: 9px; font-weight: 600; opacity: 0.75; line-height: 1;
}
.pt-cell .pt-symbol { font-size: 17px; font-weight: 700; line-height: 1.1; letter-spacing: -0.01em; }
.pt-cell .pt-mass {
    position: absolute; bottom: 3px; right: 5px;
    font-size: 8px; font-weight: 600; opacity: 0.7; line-height: 1;
}
.pt-cell.pt-cat-alkali { background: var(--pt-alkali-bg); border-color: var(--pt-alkali-bd); color: var(--pt-alkali-tx); }
.pt-cell.pt-cat-alkaline { background: var(--pt-alkaline-bg); border-color: var(--pt-alkaline-bd); color: var(--pt-alkaline-tx); }
.pt-cell.pt-cat-transition { background: var(--pt-transition-bg); border-color: var(--pt-transition-bd); color: var(--pt-transition-tx); }
.pt-cell.pt-cat-post-transition { background: var(--pt-post-bg); border-color: var(--pt-post-bd); color: var(--pt-post-tx); }
.pt-cell.pt-cat-metalloid { background: var(--pt-metalloid-bg); border-color: var(--pt-metalloid-bd); color: var(--pt-metalloid-tx); }
.pt-cell.pt-cat-nonmetal { background: var(--pt-nonmetal-bg); border-color: var(--pt-nonmetal-bd); color: var(--pt-nonmetal-tx); }
.pt-cell.pt-cat-noble-gas { background: var(--pt-noble-bg); border-color: var(--pt-noble-bd); color: var(--pt-noble-tx); }
.pt-cell.pt-cat-lanthanide { background: var(--pt-lanthanide-bg); border-color: var(--pt-lanthanide-bd); color: var(--pt-lanthanide-tx); }
.pt-cell.pt-cat-actinide { background: var(--pt-actinide-bg); border-color: var(--pt-actinide-bd); color: var(--pt-actinide-tx); }
.pt-cell.pt-cat-unknown { background: var(--pt-unknown-bg); border-color: var(--pt-unknown-bd); color: var(--pt-unknown-tx); }
.pt-cell.selected { outline: 2px solid var(--accent-1); outline-offset: 1px; z-index: 2; }
.pt-cell.dimmed { opacity: 0.22; pointer-events: none; }
.pt-fbar-label {
    display: flex; align-items: flex-end; justify-content: flex-end;
    padding: 0 8px 6px 0; font-size: 10px; font-weight: 700; color: var(--text-faint);
    letter-spacing: 0.04em; white-space: nowrap;
}
.pt-cat-badge {
    display: inline-flex; align-items: center; gap: 7px;
    border: 1px solid var(--border); background: var(--card);
    border-radius: 999px; padding: 5px 13px 5px 8px;
    font-family: inherit; font-size: 0.8rem; font-weight: 600; color: var(--text-dim);
    cursor: pointer; transition: all 0.15s ease;
}
.pt-cat-badge:hover { color: var(--text); border-color: var(--border-strong); }
.pt-cat-badge .dot { width: 11px; height: 11px; border-radius: 3px; flex: none; }
.pt-cat-badge .dot.dot-alkali { background: var(--pt-alkali-bg); border: 1px solid var(--pt-alkali-bd); }
.pt-cat-badge .dot.dot-alkaline { background: var(--pt-alkaline-bg); border: 1px solid var(--pt-alkaline-bd); }
.pt-cat-badge .dot.dot-transition { background: var(--pt-transition-bg); border: 1px solid var(--pt-transition-bd); }
.pt-cat-badge .dot.dot-post-transition { background: var(--pt-post-bg); border: 1px solid var(--pt-post-bd); }
.pt-cat-badge .dot.dot-metalloid { background: var(--pt-metalloid-bg); border: 1px solid var(--pt-metalloid-bd); }
.pt-cat-badge .dot.dot-nonmetal { background: var(--pt-nonmetal-bg); border: 1px solid var(--pt-nonmetal-bd); }
.pt-cat-badge .dot.dot-noble-gas { background: var(--pt-noble-bg); border: 1px solid var(--pt-noble-bd); }
.pt-cat-badge .dot.dot-lanthanide { background: var(--pt-lanthanide-bg); border: 1px solid var(--pt-lanthanide-bd); }
.pt-cat-badge .dot.dot-actinide { background: var(--pt-actinide-bg); border: 1px solid var(--pt-actinide-bd); }
.pt-cat-badge .dot.dot-unknown { background: var(--pt-unknown-bg); border: 1px solid var(--pt-unknown-bd); }
.pt-cat-badge.active { border-color: var(--accent-3); background: var(--accent-soft); color: var(--accent-1); }
.pt-tint-alkali { background: var(--pt-alkali-bg); border: 1px solid var(--pt-alkali-bd); color: var(--pt-alkali-tx); }
.pt-tint-alkaline { background: var(--pt-alkaline-bg); border: 1px solid var(--pt-alkaline-bd); color: var(--pt-alkaline-tx); }
.pt-tint-transition { background: var(--pt-transition-bg); border: 1px solid var(--pt-transition-bd); color: var(--pt-transition-tx); }
.pt-tint-post { background: var(--pt-post-bg); border: 1px solid var(--pt-post-bd); color: var(--pt-post-tx); }
.pt-tint-metalloid { background: var(--pt-metalloid-bg); border: 1px solid var(--pt-metalloid-bd); color: var(--pt-metalloid-tx); }
.pt-tint-nonmetal { background: var(--pt-nonmetal-bg); border: 1px solid var(--pt-nonmetal-bd); color: var(--pt-nonmetal-tx); }
.pt-tint-noble { background: var(--pt-noble-bg); border: 1px solid var(--pt-noble-bd); color: var(--pt-noble-tx); }
.pt-tint-lanthanide { background: var(--pt-lanthanide-bg); border: 1px solid var(--pt-lanthanide-bd); color: var(--pt-lanthanide-tx); }
.pt-tint-actinide { background: var(--pt-actinide-bg); border: 1px solid var(--pt-actinide-bd); color: var(--pt-actinide-tx); }
.pt-tint-unknown { background: var(--pt-unknown-bg); border: 1px solid var(--pt-unknown-bd); color: var(--pt-unknown-tx); }
.unit-inline { color: var(--text-dim); font-weight: 600; font-size: 0.8em; }
.legend-label { font-size: 0.78rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; color: var(--text-faint); margin-bottom: 8px; }
.pt-layout { display: grid; grid-template-columns: minmax(0, 1fr) 350px; gap: 22px; align-items: start; margin-top: 6px; }
.pt-board { min-width: 0; }
.pt-detail { position: sticky; top: 84px; }
.pt-detail .card { margin-bottom: 0; padding: 20px; }
.pt-hero { display: flex; align-items: center; gap: 16px; margin-bottom: 14px; }
.pt-hero-symbol {
    flex: none; width: 74px; height: 74px; border-radius: 0.9rem;
    display: flex; align-items: center; justify-content: center;
    font-size: 2rem; font-weight: 800; letter-spacing: -0.01em;
}
.pt-hero-name { font-size: 1.35rem; font-weight: 800; letter-spacing: -0.01em; line-height: 1.2; }
.pt-hero-en { font-size: 0.85rem; color: var(--text-faint); font-weight: 500; }
.pt-hero-cat {
    display: inline-block; margin-top: 4px; padding: 2px 10px; border-radius: 999px;
    font-size: 0.72rem; font-weight: 700;
}
.pt-hint { color: var(--text-faint); font-size: 0.9rem; }
.dl { display: grid; grid-template-columns: minmax(120px, auto) 1fr; gap: 2px 16px; font-size: 0.88rem; border-top: 1px solid var(--border); padding-top: 10px; }
.dl dt { color: var(--text-dim); font-weight: 600; padding: 5px 0; }
.dl dd { padding: 5px 0; text-align: right; font-weight: 500; word-break: break-word; }
.dl dd.val-accent { color: var(--accent-1); font-weight: 700; }
.shell-dots { display: inline-flex; gap: 3px; flex-wrap: wrap; justify-content: flex-end; }
.shell-dots span {
    min-width: 22px; text-align: center; padding: 1px 4px;
    background: var(--bg-soft); border: 1px solid var(--border);
    border-radius: 5px; font-weight: 700; font-size: 0.78rem; color: var(--text-dim);
}

/* ---------- tables ---------- */
.table-wrap { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 0.9rem; }
.data-table th, .data-table td { padding: 9px 12px; text-align: left; border-bottom: 1px solid var(--border); vertical-align: middle; }
.data-table th { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-faint); white-space: nowrap; }
.data-table tr:last-child td { border-bottom: none; }
.data-table .num { text-align: right; font-variant-numeric: tabular-nums; }
.data-table tfoot td { border-top: 1px solid var(--border-strong); border-bottom: none; font-weight: 800; font-size: 1rem; }
.data-table tfoot .num { color: var(--accent-1); }
.detail-cell-symbol { font-weight: 700; white-space: nowrap; }
.bar-cell { width: 120px; }
.bar-track { background: var(--bg-soft); border-radius: 4px; height: 7px; width: 100%; overflow: hidden; }
.bar-fill { background: var(--accent-1); height: 100%; border-radius: 4px; }
.sample-chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 4px; }
.sample-chips .chip { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 0.85rem; }
.sample-chips .chip sub { font-size: 0.75em; }

/* ---------- split layouts ---------- */
.split-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.split-grid .card { margin-bottom: 0; }
.tri-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 16px; }
.tri-grid .card { margin-bottom: 0; }
.two-col { display: grid; grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr); gap: 20px; align-items: start; }
.two-col .card { margin-bottom: 0; }
.result-stack { display: flex; flex-direction: column; gap: 12px; }
.step-formula { font-size: 0.95rem; color: var(--text-dim); }
.step-formula sub { font-size: 0.72em; }
.copy-btn {
    display: inline-flex; align-items: center; gap: 6px;
    border: 1px solid var(--border); background: var(--card);
    border-radius: 0.5rem; padding: 6px 12px; margin-left: auto;
    font-family: inherit; font-size: 0.78rem; font-weight: 600; color: var(--text-dim);
    cursor: pointer; transition: all 0.15s ease;
}
.copy-btn:hover { color: var(--accent-1); border-color: var(--accent-3); }
.copy-btn.copied { color: var(--good); border-color: var(--good); background: var(--good-soft); }

/* ---------- footer ---------- */
.site-footer { border-top: 1px solid var(--border); margin-top: 36px; background: var(--card); }
.footer-inner { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; padding: 26px 0; }
.footer-tag { font-size: 0.85rem; color: var(--text-dim); margin-top: 4px; }
.footer-meta { font-size: 0.78rem; color: var(--text-faint); max-width: 480px; text-align: right; line-height: 1.8; }
.footer-meta a { color: var(--text-faint); }
.footer-meta a:hover { color: var(--accent-1); }

/* ---------- responsive ---------- */
@media (max-width: 980px) {
    .pt-layout { grid-template-columns: 1fr; }
    .pt-detail { position: static; }
}
@media (max-width: 720px) {
    .nav { height: auto; flex-wrap: wrap; padding: 10px 0; }
    .nav-links { order: 3; width: 100%; justify-content: center; }
    .page-head { padding: 28px 0 4px; }
    .result-side { margin-left: 0; text-align: left; }
    .footer-inner { flex-direction: column; text-align: center; }
    .footer-meta { text-align: center; }
    .two-col { grid-template-columns: 1fr; }
    .pt-detail .pt-hero-symbol { width: 62px; height: 62px; font-size: 1.7rem; }
    .pt-wrap { margin: 0 -3vw; padding: 0 3vw; }
}
@media (max-width: 480px) {
    :root { --cell-h: 46px; }
    .pt-cell .pt-symbol { font-size: 15px; }
}