/* ===== CSS VARIABLES ===== */
:root {
  --green: #4ade80;
  --green-dim: #22c55e;
  --green-glow: rgba(74, 222, 128, 0.18);
  --green-glow-strong: rgba(74, 222, 128, 0.32);

  /* Dark theme (default) */
  --bg-base: #0d0f0d;
  --bg-mesh1: #0f1a10;
  --bg-mesh2: #0a120b;
  --bg-card: rgba(18, 22, 18, 0.85);
  --bg-card-border: rgba(74, 222, 128, 0.13);
  --bg-input: rgba(255,255,255,0.05);
  --bg-input-focus: rgba(74, 222, 128, 0.08);
  --bg-select: #111811;
  --bg-result: rgba(74, 222, 128, 0.07);
  --bg-ref: rgba(255,255,255,0.03);
  --bg-unit-pill: rgba(255,255,255,0.04);
  --text-primary: #f0fff4;
  --text-secondary: #9ca89e;
  --text-muted: #5a6b5c;
  --text-accent: #4ade80;
  --border-subtle: rgba(255,255,255,0.07);
  --border-card: rgba(74, 222, 128, 0.15);
  --shadow-card: 0 8px 40px rgba(0,0,0,0.5), 0 0 0 1px rgba(74,222,128,0.07);
  --shadow-green: 0 0 20px rgba(74,222,128,0.15);
}

[data-theme="light"] {
  --bg-base: #f0faf2;
  --bg-mesh1: #e8f5eb;
  --bg-mesh2: #f5fff7;
  --bg-card: rgba(255, 255, 255, 0.92);
  --bg-card-border: rgba(34, 197, 94, 0.2);
  --bg-input: rgba(0,0,0,0.04);
  --bg-input-focus: rgba(34, 197, 94, 0.07);
  --bg-select: #ffffff;
  --bg-result: rgba(34, 197, 94, 0.08);
  --bg-ref: rgba(0,0,0,0.02);
  --bg-unit-pill: rgba(0,0,0,0.04);
  --text-primary: #0d1f10;
  --text-secondary: #3d5c42;
  --text-muted: #7a9c7f;
  --text-accent: #16a34a;
  --border-subtle: rgba(0,0,0,0.07);
  --border-card: rgba(34, 197, 94, 0.25);
  --shadow-card: 0 8px 40px rgba(0,0,0,0.08), 0 0 0 1px rgba(34,197,94,0.1);
  --shadow-green: 0 0 20px rgba(34,197,94,0.1);
  --green: #16a34a;
  --green-dim: #22c55e;
  --green-glow: rgba(34, 197, 94, 0.12);
}

/* ===== RESET ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: 'Syne', sans-serif;
  background: var(--bg-base);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  transition: background 0.35s, color 0.35s;
  position: relative;
}

/* ===== BACKGROUND MESH ===== */
.bg-mesh {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(ellipse 60% 40% at 20% 10%, var(--green-glow) 0%, transparent 60%),
    radial-gradient(ellipse 50% 35% at 80% 80%, var(--green-glow) 0%, transparent 60%),
    radial-gradient(ellipse 30% 25% at 50% 50%, rgba(74,222,128,0.04) 0%, transparent 70%);
  transition: background 0.35s;
}

/* ===== HEADER ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  background: rgba(13,15,13,0.75);
  border-bottom: 1px solid var(--border-subtle);
  transition: background 0.35s, border-color 0.35s;
}

[data-theme="light"] .header {
  background: rgba(240, 250, 242, 0.8);
}

.header-inner {
  max-width: 900px;
  margin: 0 auto;
  padding: 0.9rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
}

.logo-icon {
  font-size: 1.3rem;
  color: var(--green);
  animation: spin-slow 8s linear infinite;
  display: inline-block;
}

@keyframes spin-slow {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

.logo-text {
  font-size: 0.95rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--text-primary);
  text-transform: uppercase;
}

.logo-sub {
  font-weight: 400;
  color: var(--text-secondary);
  letter-spacing: 0.04em;
}

.theme-toggle {
  background: var(--bg-input);
  border: 1px solid var(--border-subtle);
  border-radius: 50%;
  width: 38px;
  height: 38px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  color: var(--text-primary);
  transition: background 0.2s, border-color 0.2s, transform 0.2s;
}

.theme-toggle:hover {
  background: var(--green-glow);
  border-color: var(--green);
  transform: rotate(20deg);
}

/* ===== MAIN ===== */
.main {
  position: relative;
  z-index: 1;
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

/* ===== CATEGORY NAV ===== */
.category-nav {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  padding: 0.25rem 0;
}

.cat-btn {
  font-family: 'Syne', sans-serif;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  border: 1px solid var(--border-subtle);
  background: var(--bg-unit-pill);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
  white-space: nowrap;
}

.cat-btn:hover {
  border-color: var(--green);
  color: var(--green);
  background: var(--green-glow);
}

.cat-btn.active {
  background: var(--green);
  border-color: var(--green);
  color: #051005;
  box-shadow: var(--shadow-green);
}

/* ===== CONVERTER CARD ===== */
.converter-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: 20px;
  padding: 2rem;
  box-shadow: var(--shadow-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: background 0.35s, border-color 0.35s, box-shadow 0.35s;
}

.converter-header {
  margin-bottom: 1.8rem;
}

.converter-title {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 0.3rem;
}

.converter-desc {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-family: 'DM Mono', monospace;
}

/* ===== CONVERTER BODY ===== */
.converter-body {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1rem;
  align-items: center;
}

.field-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.field-label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.input-row {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.number-input {
  font-family: 'DM Mono', monospace;
  font-size: 1.4rem;
  font-weight: 500;
  color: var(--text-primary);
  background: var(--bg-input);
  border: 1px solid var(--border-subtle);
  border-radius: 12px;
  padding: 0.75rem 1rem;
  width: 100%;
  outline: none;
  transition: border-color 0.2s, background 0.2s, box-shadow 0.2s;
  -moz-appearance: textfield;
}

.number-input::-webkit-inner-spin-button,
.number-input::-webkit-outer-spin-button { -webkit-appearance: none; }

.number-input:focus {
  border-color: var(--green);
  background: var(--bg-input-focus);
  box-shadow: 0 0 0 3px var(--green-glow);
}

.result-input {
  color: var(--text-accent);
  background: var(--bg-result);
  border-color: rgba(74,222,128,0.2);
  cursor: default;
}

.unit-select {
  font-family: 'Syne', sans-serif;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-primary);
  background: var(--bg-select);
  border: 1px solid var(--border-subtle);
  border-radius: 10px;
  padding: 0.55rem 0.75rem;
  width: 100%;
  outline: none;
  cursor: pointer;
  transition: border-color 0.2s, box-shadow 0.2s;
  appearance: auto;
}

.unit-select:focus {
  border-color: var(--green);
  box-shadow: 0 0 0 3px var(--green-glow);
}

/* ===== SWAP ===== */
.swap-wrap {
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: 1.5rem;
}

.swap-btn {
  background: var(--bg-input);
  border: 1px solid var(--border-subtle);
  border-radius: 50%;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--text-secondary);
  transition: all 0.2s;
}

.swap-btn:hover {
  background: var(--green-glow);
  border-color: var(--green);
  color: var(--green);
  transform: rotate(90deg);
}

.swap-btn:active {
  transform: rotate(180deg) scale(0.92);
}

/* ===== RESULT BAR ===== */
.result-bar {
  margin-top: 1.5rem;
  background: var(--bg-result);
  border: 1px solid rgba(74,222,128,0.15);
  border-radius: 12px;
  padding: 0.9rem 1.2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.result-text {
  font-family: 'DM Mono', monospace;
  font-size: 0.88rem;
  color: var(--text-accent);
  flex: 1;
  min-width: 0;
  word-break: break-all;
}

.copy-btn {
  font-family: 'Syne', sans-serif;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--green);
  background: var(--green-glow);
  border: 1px solid rgba(74,222,128,0.25);
  border-radius: 8px;
  padding: 0.35rem 0.75rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 5px;
  transition: all 0.2s;
  white-space: nowrap;
}

.copy-btn:hover {
  background: var(--green-glow-strong);
  box-shadow: var(--shadow-green);
}

.copy-btn.copied {
  color: #fff;
  background: var(--green);
}

/* ===== RESET ===== */
.reset-btn {
  margin-top: 1rem;
  font-family: 'Syne', sans-serif;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-muted);
  background: transparent;
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
  padding: 0.45rem 1rem;
  cursor: pointer;
  transition: all 0.2s;
}

.reset-btn:hover {
  color: #f87171;
  border-color: rgba(248,113,113,0.3);
  background: rgba(248,113,113,0.06);
}

/* ===== REF CARD ===== */
.ref-card,
.all-units-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: 20px;
  padding: 1.75rem 2rem;
  box-shadow: var(--shadow-card);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: background 0.35s, border-color 0.35s;
}

.ref-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 1.25rem;
  display: flex;
  align-items: center;
  gap: 8px;
}

.ref-title::before {
  content: '';
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--green);
  box-shadow: 0 0 8px var(--green);
}

/* ===== REF TABLE ===== */
.ref-table-wrap {
  overflow-x: auto;
  border-radius: 10px;
  border: 1px solid var(--border-subtle);
}

.ref-table {
  width: 100%;
  border-collapse: collapse;
  font-family: 'DM Mono', monospace;
  font-size: 0.8rem;
}

.ref-table th {
  background: var(--bg-ref);
  color: var(--text-muted);
  font-size: 0.68rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 0.65rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--border-subtle);
}

.ref-table td {
  padding: 0.6rem 1rem;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border-subtle);
  transition: background 0.15s;
}

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

.ref-table tr:hover td {
  background: var(--green-glow);
  color: var(--text-primary);
}

.ref-table td:first-child { color: var(--text-accent); font-weight: 500; }
.ref-table td:last-child { color: var(--text-primary); }

/* ===== UNITS GRID ===== */
.units-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(170px, 1fr));
  gap: 10px;
}

.unit-pill {
  background: var(--bg-unit-pill);
  border: 1px solid var(--border-subtle);
  border-radius: 10px;
  padding: 0.6rem 0.9rem;
  cursor: pointer;
  transition: all 0.18s;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.unit-pill:hover {
  border-color: var(--green);
  background: var(--green-glow);
  transform: translateY(-2px);
  box-shadow: 0 4px 14px rgba(74,222,128,0.12);
}

.unit-pill-name {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-primary);
}

.unit-pill-abbr {
  font-family: 'DM Mono', monospace;
  font-size: 0.7rem;
  color: var(--text-accent);
}

/* ===== FOOTER ===== */
.footer {
  position: relative;
  z-index: 1;
  text-align: center;
  padding: 1.5rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border-subtle);
}

.footer strong { color: var(--green); }

/* ===== ANIMATIONS ===== */
@keyframes fadeSlideIn {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

.converter-card,
.ref-card,
.all-units-card {
  animation: fadeSlideIn 0.4s ease both;
}

.ref-card  { animation-delay: 0.05s; }
.all-units-card { animation-delay: 0.1s; }

/* ===== RESPONSIVE ===== */
@media (max-width: 640px) {
  .header-inner { padding: 0.75rem 1rem; }
  .main { padding: 1.25rem 1rem 3rem; }
  .converter-card,
  .ref-card,
  .all-units-card { padding: 1.25rem 1rem; }

  .converter-body {
    grid-template-columns: 1fr;
    grid-template-rows: auto auto auto;
  }

  .swap-wrap {
    padding-top: 0;
    transform: rotate(90deg);
  }

  .converter-title { font-size: 1.2rem; }
  .number-input { font-size: 1.1rem; }

  .category-nav { gap: 6px; }
  .cat-btn { font-size: 0.72rem; padding: 0.4rem 0.85rem; }

  .units-grid { grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); }
}

@media (max-width: 380px) {
  .units-grid { grid-template-columns: 1fr 1fr; }
  .result-bar { flex-direction: column; align-items: flex-start; }
}