/* ---------------------------------------------------------------
   EqVault — "cyanotype blueprint" design, light surface.
   Cards read like index sheets pinned to a drafting board.
   ------------------------------------------------------------- */

:root {
  /* page surfaces — light, cool blue-gray */
  --bg: #e9eef2;
  --bg-panel: #dfe7ec;
  --line: #b9c9d4;
  --line-soft: #cfdbe3;

  /* ink on the light surfaces */
  --ink-900: #16283a;
  --ink-700: #3d5568;
  --ink-500: #71889a;

  /* the "pinned paper" card face — warm, so it separates from the cool bg */
  --paper: #f7f3e9;
  --paper-dim: #e5dfce;
  --card-rule: #9fbdd1;
  --ink: #16232f;
  --ink-soft: #56636d;

  --pencil-red: #b23a30;
  --stamp-amber: #c98a2c;

  --font-display: "Space Grotesk", sans-serif;
  --font-body: "IBM Plex Sans", sans-serif;
  --font-mono: "IBM Plex Mono", monospace;

  --radius: 3px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  min-height: 100%;
  background: var(--bg);
  color: var(--ink-900);
  font-family: var(--font-body);
}

body {
  position: relative;
}

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
}

/* Graph-paper grid, faint, fixed to viewport */
.grid-overlay {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px),
    linear-gradient(var(--line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--line-soft) 1px, transparent 1px);
  background-size: 88px 88px, 88px 88px, 22px 22px, 22px 22px;
  opacity: 0.55;
}

/* ---------------- Topbar ---------------- */

.topbar {
  position: relative;
  z-index: 2;
  display: flex;
  align-items: center;
  gap: 28px;
  padding: 22px 36px;
  border-bottom: 1px solid var(--line);
  background: linear-gradient(180deg, var(--bg-panel) 0%, rgba(223,231,236,0.9) 100%);
  flex-wrap: wrap;
}

.brand { display: flex; align-items: center; gap: 12px; }

.brand-mark {
  font-family: var(--font-mono);
  font-weight: 600;
  font-size: 13px;
  letter-spacing: 0.08em;
  color: var(--bg);
  background: var(--ink-900);
  border: 1px solid var(--ink-900);
  border-radius: var(--radius);
  padding: 6px 8px;
}

.brand-text h1 {
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 700;
  margin: 0;
  letter-spacing: 0.01em;
  color: var(--ink-900);
}

.brand-sub {
  display: block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-700);
}

.search-block {
  flex: 1 1 320px;
  min-width: 240px;
}

#search {
  width: 100%;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink-900);
  font-family: var(--font-mono);
  font-size: 14px;
  padding: 11px 14px;
  outline: none;
  transition: border-color 0.15s ease, background 0.15s ease;
}

#search::placeholder { color: var(--ink-500); }

#search:focus {
  border-color: var(--ink-900);
  background: #fff;
}

.count-block {
  font-family: var(--font-mono);
  text-align: right;
  white-space: nowrap;
}

#result-count {
  font-size: 20px;
  font-weight: 600;
  color: var(--ink-900);
}

.count-label {
  display: block;
  font-size: 10px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-700);
}

/* ---------------- Layout ---------------- */

.layout {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 250px 1fr;
  gap: 0;
  max-width: 1400px;
  margin: 0 auto;
}

.sidebar {
  padding: 28px 20px;
  border-right: 1px solid var(--line);
  min-height: calc(100vh - 90px);
}

.sidebar-block { margin-bottom: 30px; }

.sidebar-title {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-700);
  margin: 0 0 12px 0;
  padding-bottom: 8px;
  border-bottom: 1px dashed var(--line);
}

.field-list { list-style: none; margin: 0; padding: 0; }
.field-list li { margin-bottom: 2px; }

.field-btn {
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius);
  color: var(--ink-900);
  font-family: var(--font-body);
  font-size: 13.5px;
  padding: 8px 10px;
  cursor: pointer;
  text-align: left;
  transition: background 0.12s ease, border-color 0.12s ease;
}

.field-btn:hover { background: var(--bg-panel); }

.field-btn.active {
  background: #fff;
  border-color: var(--ink-900);
  color: var(--ink-900);
  font-weight: 600;
}

.field-count {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--ink-500);
}

.tag-cloud { display: flex; flex-wrap: wrap; gap: 6px; }

.tag-chip {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--ink-700);
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 4px 10px;
  cursor: pointer;
  transition: all 0.12s ease;
}

.tag-chip:hover { border-color: var(--ink-700); color: var(--ink-900); }

.tag-chip.active {
  background: var(--pencil-red);
  border-color: var(--pencil-red);
  color: #fff;
}

/* ---------------- Content / filters ---------------- */

.content { padding: 28px 32px 60px; }

.active-filters {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 18px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--ink-700);
}

.active-filters-label { text-transform: uppercase; letter-spacing: 0.06em; }

#active-filter-chips { display: flex; gap: 6px; flex-wrap: wrap; }

.active-chip {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 3px 10px;
  color: var(--ink-900);
}

#clear-filters {
  background: transparent;
  border: none;
  color: var(--pencil-red);
  font-family: var(--font-mono);
  font-size: 12px;
  cursor: pointer;
  text-decoration: underline;
  padding: 0;
}

.empty-state {
  text-align: center;
  padding: 80px 20px;
  color: var(--ink-700);
  font-family: var(--font-mono);
}
.empty-sub { font-size: 12px; color: var(--ink-500); }

/* ---------------- Equation cards ---------------- */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(360px, 1fr));
  gap: 20px;
}

.eq-card--wide {
  grid-column: span 2;
}

.eq-card {
  background: var(--paper);
  color: var(--ink);
  border-radius: var(--radius);
  box-shadow: 0 8px 20px rgba(22, 35, 47, 0.12);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  border: 1px solid var(--paper-dim);
}

.eq-card-head {
  padding: 16px 18px 12px;
  border-bottom: 1px dashed var(--card-rule);
}

.eq-name {
  font-family: var(--font-display);
  font-size: 16.5px;
  font-weight: 600;
  margin: 0;
  line-height: 1.3;
}

.eq-render {
  padding: 22px 18px;
  font-size: 19px;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 64px;
  background:
    repeating-linear-gradient(0deg, transparent, transparent 21px, rgba(22,35,47,0.05) 22px);
  overflow-x: auto;
}

.eq-section { padding: 0 18px 14px; }

.eq-section h4 {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--ink-soft);
  margin: 0 0 8px 0;
}

.var-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 12.5px;
}

.var-table td {
  padding: 4px 6px;
  vertical-align: top;
  border-bottom: 1px solid var(--paper-dim);
}

.var-table tr:last-child td { border-bottom: none; }

.var-symbol {
  font-family: var(--font-mono);
  font-weight: 600;
  white-space: nowrap;
  width: 1%;
}

.var-unit {
  font-family: var(--font-mono);
  color: var(--ink-soft);
  text-align: right;
  white-space: nowrap;
  width: 1%;
}

.eq-assumptions ul {
  margin: 0;
  padding-left: 16px;
  font-size: 12.5px;
  line-height: 1.55;
}

.eq-assumptions li { margin-bottom: 4px; }

.eq-card-foot {
  margin-top: auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  padding: 12px 18px;
  border-top: 1px solid var(--paper-dim);
  background: rgba(22,35,47,0.03);
}

.eq-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
}

.eq-tags span {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--ink-soft);
  background: var(--paper-dim);
  border-radius: 999px;
  padding: 2px 8px;
}

.eq-source-toggle {
  flex-shrink: 0;
  background: transparent;
  border: 1px solid var(--ink-soft);
  color: var(--ink-soft);
  font-family: var(--font-mono);
  font-size: 10.5px;
  border-radius: 3px;
  padding: 4px 8px;
  cursor: pointer;
}

.eq-source-toggle:hover { border-color: var(--ink); color: var(--ink); }

.eq-source {
  margin: 0;
  padding: 10px 18px 14px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  color: var(--ink-soft);
  background: var(--paper-dim);
  white-space: pre-wrap;
  word-break: break-word;
}

/* ---------------- Responsive ---------------- */

@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    border-right: none;
    border-bottom: 1px solid var(--line);
    min-height: 0;
    padding: 20px;
  }
  .topbar { padding: 18px 20px; gap: 14px; }
  .content { padding: 20px 18px 48px; }
}

/* ---------------- Reduced motion ---------------- */

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}

/* ---------------- Focus visibility ---------------- */

button:focus-visible, input:focus-visible {
  outline: 2px solid var(--pencil-red);
  outline-offset: 2px;
}