/* ============================================================
   CALCHUB — core.css
   Shared design system for every page on the site.
   Extends the original theme (section 1-13) with new
   components for History, Favorites, Recents, the Quick
   Calculator, and calculator-page layout.
   ============================================================ */

:root {
  --bg:           #f0f4f8;
  --surface:      #ffffff;
  --surface-alt:  #f4f7fb;
  --border:       #e2e8f0;
  --text:         #0d1b2a;
  --text-muted:   #64748b;
  --text-light:   #94a3b8;
  --link:         #1a5f85;
  --link-hover:   #0d3f5e;

  --finance:      #1a6e3c;
  --math:         #1a4f99;
  --science:      #5a1a8a;
  --health:       #a32020;
  --education:    #b84f00;
  --tools:        #475569;

  --star:         #d99a1b;

  --shadow-xs:    0 1px 3px rgba(0,0,0,0.06);
  --shadow-sm:    0 2px 8px rgba(0,0,0,0.08);
  --shadow-md:    0 6px 20px rgba(0,0,0,0.11);

  --sp-xs:  4px;
  --sp-sm:  8px;
  --sp-md:  16px;
  --sp-lg:  24px;
  --sp-xl:  40px;
  --sp-2xl: 64px;

  --radius-sm:   6px;
  --radius-md:   10px;
  --radius-lg:   14px;
  --radius-full: 9999px;
}

[data-theme="dark"] {
  --bg:          #0d1b2a;
  --surface:     #162233;
  --surface-alt: #1c2d40;
  --border:      #253348;
  --text:        #e2e8f0;
  --text-muted:  #94a3b8;
  --text-light:  #64748b;
  --link:        #63b3d8;
  --link-hover:  #93cfee;
  --star:        #f2c14e;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  font-size: 15px;
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
}

a { color: inherit; }

/* ---------- SITE HEADER ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow-xs);
  transition: background-color 0.3s ease;
}
.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--sp-md) var(--sp-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-md);
}
.site-logo {
  font-size: 19px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.4px;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 8px;
}
.site-logo-img {
  height: 34px;
  width: auto;
  display: block;
}
.header-actions { display: flex; align-items: center; gap: var(--sp-sm); }

.header-icon-btn {
  height: 40px;
  padding: 0 var(--sp-md);
  border-radius: var(--radius-full);
  border: 1px solid var(--border);
  background-color: var(--surface-alt);
  display: flex;
  align-items: center;
  gap: 7px;
  cursor: pointer;
  color: var(--text);
  font-family: inherit;
  font-size: 13px;
  font-weight: 600;
  transition: background-color 0.2s, border-color 0.2s;
}
.header-icon-btn:hover { background-color: var(--border); }

.theme-btn {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  border: 1px solid var(--border);
  background-color: var(--surface-alt);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--text);
  transition: background-color 0.2s, border-color 0.2s;
  flex-shrink: 0;
}
.theme-btn:hover { background-color: var(--border); }
.icon { width: 18px; height: 18px; display: block; }
.sun-icon  { display: none; }
.moon-icon { display: block; }
[data-theme="dark"] .sun-icon  { display: block; }
[data-theme="dark"] .moon-icon { display: none; }

/* ---------- HERO ---------- */
.hero-section {
  background-color: #0d1b2a;
  padding: var(--sp-2xl) var(--sp-lg);
  text-align: center;
}
.hero-inner { max-width: 640px; margin: 0 auto; }
.hero-eyebrow {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 1.8px;
  text-transform: uppercase;
  color: #64748b;
  margin-bottom: var(--sp-md);
}
.hero-title {
  font-family: 'DM Serif Display', Georgia, serif;
  font-size: clamp(30px, 6vw, 52px);
  font-weight: 400;
  line-height: 1.15;
  color: #f1f5f9;
  margin-bottom: var(--sp-md);
  letter-spacing: -0.5px;
}
.hero-subtitle {
  font-size: 15px;
  color: #94a3b8;
  max-width: 480px;
  margin: 0 auto var(--sp-xl) auto;
}
.search-box { max-width: 480px; margin: 0 auto; }
.search-input {
  width: 100%;
  padding: 12px var(--sp-md);
  border-radius: var(--radius-md);
  border: 1px solid #253348;
  background-color: #162233;
  color: #e2e8f0;
  font-size: 15px;
  font-family: 'Inter', sans-serif;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.search-input::placeholder { color: #4a6080; }
.search-input:focus {
  outline: none;
  border-color: #63b3d8;
  box-shadow: 0 0 0 3px rgba(99, 179, 216, 0.15);
}

/* ---------- MAIN LAYOUT ---------- */
.main-layout { max-width: 1200px; margin: 0 auto; padding: var(--sp-xl) var(--sp-lg); }
.section-label {
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--text-light);
  margin-bottom: var(--sp-lg);
  padding-bottom: var(--sp-sm);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-sm);
}
.section-label .label-action {
  text-transform: none;
  letter-spacing: 0;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--link);
  background: none;
  border: none;
  cursor: pointer;
  font-family: inherit;
}
.section-label .label-action:hover { color: var(--link-hover); text-decoration: underline; }
.page-section { margin-bottom: var(--sp-2xl); }
.page-section:last-child { margin-bottom: var(--sp-xl); }

/* ---------- CATEGORIES GRID ---------- */
.categories-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: var(--sp-lg); }

.category-card {
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--sp-lg);
  position: relative;
  overflow: hidden;
  transition: box-shadow 0.2s ease, transform 0.2s ease, opacity 0.5s ease;
}
.category-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 4px; height: 100%;
  border-radius: var(--radius-lg) 0 0 var(--radius-lg);
}
#cat-finance::before   { background-color: var(--finance); }
#cat-math::before      { background-color: var(--math); }
#cat-science::before   { background-color: var(--science); }
#cat-health::before    { background-color: var(--health); }
#cat-education::before { background-color: var(--education); }
.category-card:hover { box-shadow: var(--shadow-md); transform: translateY(-3px); }

.fade-init { opacity: 0; transform: translateY(16px); }
.fade-in   { opacity: 1; transform: translateY(0); transition: opacity 0.5s ease, transform 0.5s ease; }

.category-header { margin-bottom: var(--sp-md); }
.category-tag {
  display: inline-block;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.3px;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  color: #ffffff;
  text-transform: uppercase;
}
.finance-tag   { background-color: var(--finance); }
.math-tag      { background-color: var(--math); }
.science-tag   { background-color: var(--science); }
.health-tag    { background-color: var(--health); }
.education-tag { background-color: var(--education); }
.tools-tag     { background-color: var(--tools); }

.calculator-list { display: flex; flex-direction: column; gap: 2px; }

.calc-row { display: flex; align-items: center; gap: 2px; border-radius: var(--radius-sm); }

.calc-link {
  flex: 1;
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
  padding: 7px var(--sp-sm);
  border-radius: var(--radius-sm);
  text-decoration: none;
  color: var(--link);
  font-size: 14px;
  font-family: 'Inter', sans-serif;
  transition: background-color 0.15s, color 0.15s, padding-left 0.15s;
}
.calc-link::before {
  content: '→';
  font-size: 12px;
  color: var(--text-light);
  opacity: 0;
  transform: translateX(-6px);
  transition: opacity 0.15s, transform 0.15s;
  flex-shrink: 0;
}
.calc-link:hover { background-color: var(--surface-alt); color: var(--link-hover); padding-left: 12px; }
.calc-link:hover::before { opacity: 1; transform: translateX(0); }

.fav-star-btn {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border: none;
  background: none;
  cursor: pointer;
  color: var(--text-light);
  font-size: 15px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color 0.15s, transform 0.1s;
}
.fav-star-btn:hover { color: var(--star); transform: scale(1.15); }
.fav-star-btn.is-fav { color: var(--star); }

/* ---------- FOOTER ---------- */
.site-footer {
  text-align: center;
  padding: var(--sp-xl) var(--sp-lg);
  color: var(--text-light);
  font-size: 13px;
  border-top: 1px solid var(--border);
  margin-top: var(--sp-xl);
}

/* ============================================================
   FAVORITES / RECENTS (homepage)
   ============================================================ */
.pill-list { display: flex; flex-direction: column; gap: 6px; }
.pill-row {
  display: flex;
  align-items: center;
  gap: var(--sp-sm);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 10px var(--sp-md);
  transition: box-shadow 0.15s, transform 0.15s;
}
.pill-row:hover { box-shadow: var(--shadow-sm); transform: translateY(-1px); }
.pill-dot { width: 8px; height: 8px; border-radius: 50%; flex-shrink: 0; }
.pill-link { flex: 1; text-decoration: none; color: var(--text); font-size: 14px; font-weight: 500; }
.pill-link:hover { color: var(--link); }
.pill-meta { font-size: 12px; color: var(--text-light); flex-shrink: 0; }
.pill-row .fav-star-btn { width: 24px; height: 24px; font-size: 14px; }

.grid-2col { display: grid; grid-template-columns: 1fr 1fr; gap: var(--sp-lg); align-items: start; }

.empty-state {
  border: 1px dashed var(--border);
  border-radius: var(--radius-md);
  padding: var(--sp-lg);
  text-align: center;
  color: var(--text-light);
  font-size: 13.5px;
}

/* ============================================================
   HISTORY PANEL
   ============================================================ */
.history-panel { display: flex; flex-direction: column; gap: 8px; }
.history-toolbar { display: flex; justify-content: flex-end; margin-bottom: 4px; }
.history-list { display: flex; flex-direction: column; gap: 8px; max-height: 480px; overflow-y: auto; padding-right: 2px; }
.history-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 10px 12px;
  display: flex;
  align-items: center;
  gap: 10px;
  transition: box-shadow 0.15s;
}
.history-item:hover { box-shadow: var(--shadow-sm); }
.history-item-main { flex: 1; min-width: 0; }
.history-item-label {
  font-size: 13.5px;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.history-item-meta { display: flex; align-items: center; gap: 6px; margin-top: 3px; }
.history-item-time { font-size: 11.5px; color: var(--text-light); }
.badge-category {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.3px;
  text-transform: uppercase;
  padding: 2px 7px;
  border-radius: var(--radius-full);
  color: #fff;
  flex-shrink: 0;
}
.badge-finance   { background: var(--finance); }
.badge-math      { background: var(--math); }
.badge-science   { background: var(--science); }
.badge-health    { background: var(--health); }
.badge-education { background: var(--education); }
.badge-tools     { background: var(--tools); }

.history-item-actions { display: flex; gap: 4px; flex-shrink: 0; }
.icon-btn {
  width: 30px; height: 30px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--surface-alt);
  color: var(--text-muted);
  cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  transition: background-color 0.15s, color 0.15s;
}
.icon-btn:hover { background: var(--border); color: var(--text); }
.icon-btn.danger:hover { background: #fde2e2; color: #a32020; }
[data-theme="dark"] .icon-btn.danger:hover { background: #3a1a1a; color: #f2a3a3; }
.icon-btn svg { width: 14px; height: 14px; }

.btn-text-small {
  background: none; border: none; cursor: pointer;
  color: var(--text-muted); font-size: 12.5px; font-weight: 600;
  font-family: inherit; padding: 4px 8px; border-radius: var(--radius-sm);
}
.btn-text-small:hover { color: #a32020; background: var(--surface-alt); }

/* ============================================================
   CALCULATOR PAGE LAYOUT
   ============================================================ */
.breadcrumb { font-size: 12.5px; color: var(--text-light); margin-bottom: var(--sp-lg); display: flex; gap: 6px; flex-wrap: wrap; }
.breadcrumb a { color: var(--text-muted); text-decoration: none; }
.breadcrumb a:hover { color: var(--link); text-decoration: underline; }

.calc-page-header { display: flex; align-items: center; justify-content: space-between; gap: var(--sp-md); margin-bottom: 6px; }
.calc-page-title { font-family: 'DM Serif Display', Georgia, serif; font-size: clamp(24px, 4vw, 32px); font-weight: 400; }
.calc-page-intro { color: var(--text-muted); font-size: 14px; max-width: 640px; margin-bottom: var(--sp-xl); }

.fav-star-btn.large { width: 42px; height: 42px; font-size: 21px; border: 1px solid var(--border); background: var(--surface); flex-shrink: 0; }

.calc-layout { display: grid; grid-template-columns: minmax(0,1.15fr) minmax(0,0.85fr); gap: var(--sp-xl); align-items: start; }

.calc-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: var(--sp-lg);
}
.calc-card + .calc-card { margin-top: var(--sp-lg); }
.calc-card-title {
  font-size: 12.5px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  color: var(--text-light);
  margin-bottom: var(--sp-md);
}

.field-grid { display: grid; grid-template-columns: 1fr 1fr; gap: var(--sp-md); margin-bottom: var(--sp-md); }
.field-group { display: flex; flex-direction: column; gap: 6px; min-width: 0; }
.field-group.span-2 { grid-column: 1 / -1; }
.field-label { font-size: 12.5px; font-weight: 600; color: var(--text-muted); }
.field-input, .field-select {
  width: 100%;
  padding: 10px 12px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  background: var(--surface-alt);
  color: var(--text);
  font-size: 14.5px;
  font-family: inherit;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.field-input:focus, .field-select:focus {
  outline: none;
  border-color: var(--link);
  box-shadow: 0 0 0 3px rgba(26, 95, 133, 0.13);
}
.field-hint { font-size: 11.5px; color: var(--text-light); }

.btn-primary {
  width: 100%;
  padding: 12px var(--sp-md);
  border-radius: var(--radius-md);
  border: none;
  background: var(--link);
  color: #fff;
  font-size: 14.5px;
  font-weight: 700;
  font-family: inherit;
  cursor: pointer;
  transition: background-color 0.15s, transform 0.1s;
  margin-top: 4px;
}
.btn-primary:hover { background: var(--link-hover); }
.btn-primary:active { transform: scale(0.98); }

.result-panel { display: none; }
.result-panel.visible { display: block; }
.result-headline-label { font-size: 12px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.5px; color: var(--text-light); margin-bottom: 4px; }
.result-headline { font-family: 'DM Serif Display', Georgia, serif; font-size: clamp(26px, 4vw, 38px); color: var(--text); margin-bottom: var(--sp-lg); word-break: break-word; }
.stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 10px; }
.stat-card { background: var(--surface-alt); border-radius: var(--radius-md); padding: 12px 14px; border: 1px solid var(--border); }
.stat-card-label { font-size: 11px; color: var(--text-light); text-transform: uppercase; letter-spacing: 0.3px; font-weight: 600; margin-bottom: 3px; }
.stat-card-value { font-size: 16.5px; font-weight: 700; color: var(--text); }
.stat-card.highlight { background: color-mix(in srgb, var(--link) 10%, var(--surface-alt)); border-color: var(--link); }

.chart-wrap { position: relative; width: 100%; height: 220px; }
.chart-wrap canvas { width: 100% !important; height: 100% !important; }
.chart-legend { display: flex; flex-wrap: wrap; gap: 10px 16px; margin-top: var(--sp-md); }
.chart-legend-item { display: flex; align-items: center; gap: 6px; font-size: 12.5px; color: var(--text-muted); }
.chart-legend-swatch { width: 10px; height: 10px; border-radius: 3px; flex-shrink: 0; }

/* ---------- keypad (quick calculator + scientific calculator) ---------- */
.keypad-display {
  background: #0d1b2a;
  color: #f1f5f9;
  border-radius: var(--radius-md);
  padding: 18px 16px;
  text-align: right;
  margin-bottom: var(--sp-md);
}
.keypad-expression { font-size: 12.5px; color: #7fa8c9; min-height: 16px; word-break: break-all; }
.keypad-result { font-size: 30px; font-weight: 600; word-break: break-all; font-family: 'DM Serif Display', Georgia, serif; }
.keypad-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.keypad-grid.scientific { grid-template-columns: repeat(5, 1fr); }
.key-btn {
  padding: 14px 4px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border);
  background: var(--surface-alt);
  color: var(--text);
  font-size: 15px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background-color 0.1s, transform 0.05s;
}
.key-btn:hover { background: var(--border); }
.key-btn:active { transform: scale(0.95); }
.key-btn.op { background: var(--link); color: #fff; }
.key-btn.op:hover { background: var(--link-hover); }
.key-btn.equals { background: var(--finance); color: #fff; }
.key-btn.equals:hover { background: #124f2a; }
.key-btn.clear { background: #a32020; color: #fff; }
.key-btn.clear:hover { background: #7c1818; }
.key-btn.fn { font-size: 12.5px; }

/* ---------- dynamic row tools (GPA / admissions tracker) ---------- */
.row-table { display: flex; flex-direction: column; gap: 8px; margin-bottom: var(--sp-md); }
.row-item { display: grid; grid-template-columns: 1.6fr 1fr 0.8fr auto; gap: 8px; align-items: center; }
.row-item input, .row-item select { padding: 9px 10px; }
.row-remove-btn {
  width: 34px; height: 34px; border-radius: var(--radius-md);
  border: 1px solid var(--border); background: var(--surface-alt);
  color: var(--text-muted); cursor: pointer; flex-shrink: 0;
  display: flex; align-items: center; justify-content: center; font-size: 16px;
}
.row-remove-btn:hover { background: #fde2e2; color: #a32020; }
.btn-secondary {
  padding: 9px 14px; border-radius: var(--radius-md);
  border: 1px dashed var(--border); background: none;
  color: var(--link); font-weight: 600; font-size: 13px;
  cursor: pointer; font-family: inherit; width: 100%;
}
.btn-secondary:hover { background: var(--surface-alt); border-style: solid; }

/* ---------- toast ---------- */
.toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: #0d1b2a;
  color: #f1f5f9;
  padding: 11px 20px;
  border-radius: var(--radius-full);
  font-size: 13.5px;
  font-weight: 600;
  box-shadow: var(--shadow-md);
  z-index: 999;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease, transform 0.2s ease;
}
.toast.visible { opacity: 1; transform: translateX(-50%) translateY(0); }

/* ---------- RESPONSIVE ---------- */
@media (max-width: 860px) {
  .calc-layout { grid-template-columns: 1fr; }
  .grid-2col { grid-template-columns: 1fr; }
}
@media (max-width: 768px) {
  .categories-grid { grid-template-columns: 1fr; }
  .hero-section { padding: var(--sp-xl) var(--sp-md); }
  .main-layout { padding: var(--sp-lg) var(--sp-md); }
  .field-grid { grid-template-columns: 1fr; }
  .row-item { grid-template-columns: 1fr; }
}
@media (max-width: 480px) {
  .header-inner { padding: var(--sp-md); }
  .hero-title { font-size: 28px; }
  .header-actions .header-icon-btn span { display: none; }
  .header-icon-btn { width: 40px; padding: 0; justify-content: center; }
}

/* ---------- SHARE / EMBED / EXPLAIN (added) ---------- */
.share-embed-row { display: flex; gap: 8px; margin-top: 10px; flex-wrap: wrap; }
.btn-secondary {
  height: 36px; padding: 0 14px; border-radius: var(--radius-full);
  border: 1px solid var(--border); background: var(--surface-alt);
  color: var(--text); font-family: inherit; font-size: 12.5px; font-weight: 600;
  cursor: pointer;
}
.btn-secondary:hover { background: var(--border); }
.result-explain {
  margin-top: 14px; padding-top: 14px; border-top: 1px solid var(--border);
  font-size: 13.5px; color: var(--text-muted); line-height: 1.6;
}

/* ---------- CALCULATOR EXPLAINER CONTENT (added) ---------- */
.calc-explainer {
  margin-top: var(--sp-xl);
  padding-top: var(--sp-lg);
  border-top: 1px solid var(--border);
}
.calc-explainer h2 {
  font-size: 17px;
  font-weight: 700;
  margin: 22px 0 8px;
  color: var(--text);
}
.calc-explainer h2:first-child { margin-top: 0; }
.calc-explainer p {
  font-size: 14.5px;
  line-height: 1.7;
  color: var(--text-muted);
  margin-bottom: 10px;
  max-width: 68ch;
}
.calc-explainer strong { color: var(--text); }

/* ---------- FOOTER CONTACT / SIGNOFF (added) ---------- */
.footer-contact { font-size: 12.5px; color: var(--text-light); margin-top: 6px; }
.footer-contact a { color: var(--link); text-decoration: none; }
.footer-contact a:hover { text-decoration: underline; }
.footer-signoff { font-size: 12.5px; color: var(--text-light); margin-top: 4px; font-style: italic; }