/* ==========================================================================
   CalcMate — design tokens
   Concept: "Ledger & Tape" — graph-paper precision + measuring-instrument
   brass/steel/plum/forest palette. IBM Plex Sans for text, IBM Plex Mono
   for every number the tools produce (dial-readout feel + real tabular
   alignment for calculator output).
   ========================================================================== */

:root {
  /* Paper */
  --paper: #EEF1EF;
  --paper-card: #FFFFFF;
  --grid-line: rgba(27, 36, 48, 0.07);

  /* Ink */
  --ink: #1B2430;
  --ink-soft: #5B6570;
  --ink-faint: #8B94A0;

  /* Brand */
  --brass: #B7862C;
  --brass-dark: #8F6A22;
  --brass-tint: #F3E7CE;

  /* Category colors — Unit / Age / Loan */
  --steel: #2D6E8E;
  --steel-tint: #E1EDF2;
  --plum: #7C4A6B;
  --plum-tint: #F0E4EC;
  --forest: #2F6E4F;
  --forest-tint: #E1EEE6;

  --alert: #B23A34;
  --border: #DDE2DE;

  --font-display: 'IBM Plex Sans', -apple-system, sans-serif;
  --font-body: 'IBM Plex Sans', -apple-system, sans-serif;
  --font-mono: 'IBM Plex Mono', 'Courier New', monospace;

  --radius: 6px;
  --shadow-card: 0 1px 2px rgba(27,36,48,0.06), 0 1px 12px rgba(27,36,48,0.05);
  --shadow-lift: 0 8px 24px rgba(27,36,48,0.10);
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-body);
  color: var(--ink);
  background:
    linear-gradient(var(--grid-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-line) 1px, transparent 1px),
    var(--paper);
  background-size: 28px 28px, 28px 28px, 100% 100%;
  line-height: 1.6;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  color: var(--ink);
  line-height: 1.2;
  margin: 0 0 0.5em 0;
  font-weight: 600;
  letter-spacing: -0.01em;
}
h1 { font-size: clamp(2rem, 4vw, 2.75rem); font-weight: 700; }
h2 { font-size: clamp(1.4rem, 2.6vw, 1.85rem); }
h3 { font-size: 1.2rem; }
p { margin: 0 0 1em 0; color: var(--ink); }
a { color: var(--steel); text-decoration: none; }
a:hover { text-decoration: underline; }
a:focus-visible, button:focus-visible, input:focus-visible, select:focus-visible {
  outline: 2px solid var(--brass);
  outline-offset: 2px;
}

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px; }
.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--brass-dark);
  font-weight: 600;
}

/* ---------- Header ---------- */
.site-header {
  border-bottom: 1px solid var(--border);
  background: rgba(238,241,239,0.9);
  backdrop-filter: blur(6px);
  position: sticky; top: 0; z-index: 40;
}
.site-header .wrap { display: flex; align-items: center; justify-content: space-between; height: 66px; }
.logo { display: flex; align-items: center; gap: 8px; font-family: var(--font-display); font-weight: 700; font-size: 1.15rem; color: var(--ink); }
.logo .mark { color: var(--brass); font-family: var(--font-mono); }
.site-nav { display: flex; gap: 28px; font-size: 0.95rem; font-weight: 500; }
.site-nav a { color: var(--ink-soft); }
.site-nav a.active, .site-nav a:hover { color: var(--ink); text-decoration: none; }

/* ---------- Ruler-tick divider (signature element) ---------- */
.ruler {
  width: 100%; height: 22px; display: block;
  color: var(--ink-faint);
  margin: 0;
}
.ruler-section { margin: 64px 0; }

/* ---------- Hero / Tool ---------- */
.hero { padding: 52px 0 8px; }
.hero-head { max-width: 640px; margin-bottom: 32px; }
.hero-head h1 { margin-bottom: 14px; }
.hero-head p { color: var(--ink-soft); font-size: 1.05rem; }

.tool-card {
  background: var(--paper-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-card);
  overflow: hidden;
}
.tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
  background: #F7F8F6;
}
.tab-btn {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  letter-spacing: 0.03em;
  text-transform: uppercase;
  font-weight: 600;
  color: var(--ink-soft);
  background: none;
  border: none;
  padding: 16px 20px;
  cursor: pointer;
  border-bottom: 3px solid transparent;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: color 0.15s ease, border-color 0.15s ease;
}
.tab-btn:hover { color: var(--ink); }
.tab-btn[aria-selected="true"] { color: var(--ink); }
.tab-btn[data-tab="unit"][aria-selected="true"] { border-color: var(--steel); }
.tab-btn[data-tab="age"][aria-selected="true"] { border-color: var(--plum); }
.tab-btn[data-tab="loan"][aria-selected="true"] { border-color: var(--forest); }
.tab-dot { width: 7px; height: 7px; border-radius: 50%; }
.tab-btn[data-tab="unit"] .tab-dot { background: var(--steel); }
.tab-btn[data-tab="age"] .tab-dot { background: var(--plum); }
.tab-btn[data-tab="loan"] .tab-dot { background: var(--forest); }

.tab-panel { display: none; padding: 32px; }
.tab-panel.active { display: block; }

.field-row { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-bottom: 16px; }
.field { display: flex; flex-direction: column; gap: 6px; }
.field label { font-size: 0.8rem; font-weight: 600; color: var(--ink-soft); }
.field input, .field select {
  font-family: var(--font-mono);
  font-size: 1rem;
  padding: 11px 12px;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: #FCFCFB;
  color: var(--ink);
}
.field input:focus, .field select:focus { border-color: var(--brass); }

.swap-btn {
  align-self: flex-end;
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 4px;
  width: 40px; height: 40px;
  display: flex; align-items: center; justify-content: center;
  cursor: pointer;
  color: var(--ink-soft);
  margin-bottom: 2px;
}
.swap-btn:hover { color: var(--steel); border-color: var(--steel); }

.result-box {
  margin-top: 20px;
  padding: 20px;
  border-radius: 4px;
  background: var(--steel-tint);
  border: 1px solid var(--border);
}
.tab-panel[data-panel="age"] .result-box { background: var(--plum-tint); }
.tab-panel[data-panel="loan"] .result-box { background: var(--forest-tint); }
.result-label { font-size: 0.78rem; color: var(--ink-soft); font-weight: 600; margin-bottom: 4px; }
.result-value { font-family: var(--font-mono); font-size: 1.9rem; font-weight: 600; color: var(--ink); }
.result-sub { font-family: var(--font-mono); font-size: 0.88rem; color: var(--ink-soft); margin-top: 6px; }
.result-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin-top: 14px; }
.result-grid .result-box { margin-top: 0; }
.result-grid .result-value { font-size: 1.4rem; }

/* ---------- Buttons ---------- */
.btn {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.95rem;
  padding: 11px 22px;
  border-radius: 4px;
  border: 1px solid var(--brass);
  background: var(--brass);
  color: #FFFDF7;
  cursor: pointer;
  display: inline-flex; align-items: center; gap: 8px;
}
.btn:hover { background: var(--brass-dark); border-color: var(--brass-dark); }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--border); }
.btn-ghost:hover { border-color: var(--ink-soft); background: transparent; }

/* ---------- Sections / Article grid ---------- */
.section-head { display: flex; align-items: baseline; justify-content: space-between; margin-bottom: 24px; flex-wrap: wrap; gap: 8px; }
.section-head h2 { margin-bottom: 0; }
.see-all { font-family: var(--font-mono); font-size: 0.85rem; font-weight: 600; }

.card-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }

.article-card {
  background: var(--paper-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  display: flex; flex-direction: column;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  position: relative;
}
.article-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-lift); }
.article-card .thumb { width: 100%; aspect-ratio: 16/9; display: block; background: var(--paper); }
.article-card .thumb img { width: 100%; height: 100%; object-fit: cover; display: block; }
.card-tab {
  position: absolute; top: 0; left: 20px;
  font-family: var(--font-mono); font-size: 0.68rem; letter-spacing: 0.06em; text-transform: uppercase;
  font-weight: 700; color: #fff;
  padding: 4px 10px 5px;
  border-radius: 0 0 4px 4px;
}
.card-tab.unit { background: var(--steel); }
.card-tab.age { background: var(--plum); }
.card-tab.loan { background: var(--forest); }
.article-card .body { padding: 18px 20px 20px; display: flex; flex-direction: column; gap: 8px; flex: 1; }
.article-card h3 { font-size: 1.05rem; margin-bottom: 0; }
.article-card h3 a { color: var(--ink); }
.article-card h3 a:hover { color: var(--steel); text-decoration: none; }
.article-card p { color: var(--ink-soft); font-size: 0.92rem; margin: 0; flex: 1; }
.read-more { font-family: var(--font-mono); font-size: 0.8rem; font-weight: 600; color: var(--brass-dark); }

.filter-row { display: flex; gap: 10px; margin-bottom: 28px; flex-wrap: wrap; }
.filter-chip {
  font-family: var(--font-mono); font-size: 0.8rem; font-weight: 600;
  padding: 8px 16px; border-radius: 20px; border: 1px solid var(--border);
  background: var(--paper-card); color: var(--ink-soft); cursor: pointer;
}
.filter-chip.active { background: var(--ink); color: #fff; border-color: var(--ink); }

/* ---------- Why / features ---------- */
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.feature { padding: 4px 0; }
.feature .num { font-family: var(--font-mono); color: var(--brass); font-size: 0.85rem; font-weight: 700; }
.feature h3 { margin: 6px 0 6px; font-size: 1.05rem; }
.feature p { color: var(--ink-soft); font-size: 0.93rem; margin: 0; }

/* ---------- Footer ---------- */
.site-footer { border-top: 1px solid var(--border); padding: 40px 0; margin-top: 40px; }
.site-footer .wrap { display: flex; justify-content: space-between; align-items: flex-start; flex-wrap: wrap; gap: 24px; }
.footer-cols { display: flex; gap: 60px; flex-wrap: wrap; }
.footer-col h4 { font-family: var(--font-mono); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--ink-faint); margin-bottom: 10px; }
.footer-col a { display: block; color: var(--ink-soft); font-size: 0.9rem; margin-bottom: 8px; }
.footer-col a:hover { color: var(--ink); }
.footer-note { color: var(--ink-faint); font-size: 0.82rem; margin-top: 28px; }

/* ---------- Article page ---------- */
.article-header { padding: 44px 0 0; }
.breadcrumb { font-family: var(--font-mono); font-size: 0.78rem; color: var(--ink-faint); margin-bottom: 18px; }
.breadcrumb a { color: var(--ink-faint); }
.article-header .cat-label { font-family: var(--font-mono); font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.06em; padding: 4px 10px; border-radius: 3px; display: inline-block; margin-bottom: 14px; color: #fff; }
.cat-label.unit { background: var(--steel); }
.cat-label.age { background: var(--plum); }
.cat-label.loan { background: var(--forest); }
.article-header h1 { max-width: 760px; }
.article-meta { color: var(--ink-faint); font-size: 0.86rem; font-family: var(--font-mono); margin-bottom: 24px; }
.article-hero-img { width: 100%; max-width: 900px; border-radius: var(--radius); overflow: hidden; margin: 8px 0 36px; box-shadow: var(--shadow-card); }
.article-hero-img img { width: 100%; display: block; }

.article-body { max-width: 720px; }
.article-body h2 { margin-top: 1.6em; font-size: 1.35rem; }
.article-body p { color: var(--ink); font-size: 1.02rem; }
.article-body ul, .article-body ol { color: var(--ink); padding-left: 1.3em; margin-bottom: 1.2em; }
.article-body li { margin-bottom: 0.4em; }
.article-body strong { color: var(--ink); }
.article-body .formula-box {
  font-family: var(--font-mono);
  background: var(--paper-card);
  border: 1px solid var(--border);
  border-left: 3px solid var(--brass);
  padding: 14px 18px;
  border-radius: 4px;
  margin: 1.4em 0;
  font-size: 0.95rem;
  overflow-x: auto;
}

.tool-cta {
  margin: 2.2em 0;
  padding: 22px 24px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--paper-card);
  display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap;
}
.tool-cta p { margin: 0; font-weight: 500; }

.faq { margin-top: 2.4em; }
.faq-item { border-top: 1px solid var(--border); padding: 18px 0; }
.faq-item h3 { font-size: 1.02rem; margin-bottom: 8px; }
.faq-item p { color: var(--ink-soft); margin: 0; }

/* ---------- Responsive ---------- */
@media (max-width: 880px) {
  .card-grid { grid-template-columns: repeat(2, 1fr); }
  .feature-grid { grid-template-columns: 1fr; gap: 20px; }
  .field-row { grid-template-columns: 1fr; }
  .swap-btn { align-self: center; }
  .result-grid { grid-template-columns: 1fr; }
}
@media (max-width: 600px) {
  .card-grid { grid-template-columns: 1fr; }
  .tabs { overflow-x: auto; }
  .tab-btn { padding: 14px 14px; white-space: nowrap; }
  .tab-panel { padding: 22px 18px; }
  .site-footer .wrap { flex-direction: column; }
  .footer-cols { gap: 32px; }
}