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

:root {
  --bg: #0f1117;
  --surface: #1a1d2e;
  --surface2: #252840;
  --border: #2e3250;
  --accent: #6c63ff;
  --accent2: #ff6584;
  --green: #43e97b;
  --red: #ff4d6d;
  --text: #e8eaf6;
  --text2: #9294a8;
  --sop: #43e97b33;
  --sop-border: #43e97b;
  --pos: #ff6b6b33;
  --pos-border: #ff6b6b;
  --radius: 12px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: 'Segoe UI', system-ui, sans-serif;
  line-height: 1.6;
  min-height: 100vh;
}

.app {
  max-width: 1100px;
  margin: 0 auto;
  padding: 32px 20px 60px;
}

header {
  text-align: center;
  margin-bottom: 36px;
}
header h1 {
  font-size: 2.4rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--accent2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.subtitle {
  color: var(--text2);
  margin-top: 6px;
  font-size: 1rem;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 24px;
  box-shadow: var(--shadow);
}
.card h2 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text2);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 18px;
}

/* Input */
.input-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
#expr-input {
  flex: 1;
  min-width: 220px;
  background: var(--surface2);
  border: 1.5px solid var(--border);
  border-radius: 8px;
  padding: 10px 16px;
  color: var(--text);
  font-size: 1.05rem;
  font-family: 'Consolas', 'Courier New', monospace;
  outline: none;
  transition: border-color 0.2s;
}
#expr-input:focus { border-color: var(--accent); }

button {
  padding: 10px 22px;
  border-radius: 8px;
  border: none;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 600;
  transition: filter 0.15s, transform 0.1s;
}
button:hover { filter: brightness(1.15); transform: translateY(-1px); }
button:active { transform: translateY(0); }

#compute-btn {
  background: linear-gradient(135deg, var(--accent), #8b5cf6);
  color: #fff;
}
button.secondary {
  background: var(--surface2);
  color: var(--text);
  border: 1px solid var(--border);
}
button.small { padding: 6px 14px; font-size: 0.83rem; }

.operator-hints {
  margin-top: 14px;
  color: var(--text2);
  font-size: 0.88rem;
}
.operator-hints kbd {
  display: inline-block;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  font-family: monospace;
  font-size: 0.85em;
  color: var(--text);
  margin: 0 2px;
}

.examples {
  margin-top: 10px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  font-size: 0.85rem;
  color: var(--text2);
}
.example-btn {
  padding: 4px 12px;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 20px;
  color: var(--accent);
  font-size: 0.82rem;
  font-family: monospace;
  font-weight: 500;
}

.error {
  background: #ff4d6d22;
  border: 1px solid var(--red);
  border-radius: 8px;
  padding: 10px 16px;
  margin-top: 14px;
  color: var(--red);
  font-size: 0.9rem;
}
.hidden { display: none !important; }

/* Truth Table */
.table-controls { margin-bottom: 12px; }
.table-wrapper { overflow-x: auto; }
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
}
th {
  background: var(--surface2);
  color: var(--accent);
  font-weight: 700;
  padding: 10px 16px;
  text-align: center;
  border-bottom: 2px solid var(--border);
  letter-spacing: 0.05em;
}
td {
  padding: 8px 16px;
  text-align: center;
  border-bottom: 1px solid var(--border);
  font-family: 'Consolas', monospace;
  color: var(--text);
}
tr:last-child td { border-bottom: none; }
tr.row-one td:last-child { color: var(--green); font-weight: 700; }
tr.row-zero td:last-child { color: var(--red); opacity: 0.8; }
tr:hover td { background: var(--surface2); }

/* K-map */
#kmap-container {
  overflow-x: auto;
}
.kmap-note {
  color: var(--text2);
  font-size: 0.88rem;
  margin-top: 12px;
}

.kmap-wrap {
  display: inline-flex;
  flex-direction: column;
  align-items: flex-start;
}

.kmap-table {
  border-collapse: collapse;
  margin-top: 4px;
}
.kmap-table th, .kmap-table td {
  border: 1.5px solid var(--border);
  width: 64px;
  height: 56px;
  text-align: center;
  vertical-align: middle;
  padding: 0;
  font-family: 'Consolas', monospace;
}
.kmap-table th {
  background: var(--surface2);
  color: var(--text2);
  font-size: 0.82rem;
  font-weight: 600;
  width: 64px;
  min-width: 64px;
}
.kmap-table td {
  font-size: 1.1rem;
  font-weight: 700;
  cursor: default;
  position: relative;
  transition: background 0.2s;
}
.kmap-table td.val-1 { color: var(--green); }
.kmap-table td.val-0 { color: var(--red); opacity: 0.6; }
.kmap-table td.grp-sop { background: var(--sop); }
.kmap-table td.grp-pos { background: var(--pos); }
.kmap-table td.grp-sop.grp-pos { background: linear-gradient(135deg, var(--sop) 50%, var(--pos) 50%); }

.kmap-corner { background: var(--surface) !important; border: none !important; }
.kmap-var-label {
  font-size: 0.82rem;
  color: var(--text2);
  margin-bottom: 2px;
  text-align: left;
  padding-left: 68px;
}

.kmap-legend {
  display: flex;
  gap: 20px;
  margin-top: 14px;
  font-size: 0.85rem;
}
.legend-item { display: flex; align-items: center; gap: 6px; }
.sop-color { color: var(--green); }
.pos-color { color: #ff6b6b; }

/* Results */
.results-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}
@media (max-width: 600px) { .results-grid { grid-template-columns: 1fr; } }

.result-box {
  border-radius: 10px;
  padding: 20px;
  position: relative;
}
.sop-box {
  background: #43e97b11;
  border: 1.5px solid var(--sop-border);
}
.pos-box {
  background: #ff6b6b11;
  border: 1.5px solid var(--pos-border);
}
.result-box h3 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.sop-box h3 { color: var(--green); }
.pos-box h3 { color: #ff6b6b; }
.tag {
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--text2);
  background: var(--surface2);
  border-radius: 12px;
  padding: 2px 8px;
}
.formula {
  font-family: 'Consolas', 'Courier New', monospace;
  font-size: 1rem;
  color: var(--text);
  min-height: 28px;
  word-break: break-all;
  margin-bottom: 12px;
}
.copy-btn {
  padding: 5px 14px;
  font-size: 0.8rem;
  background: var(--surface2);
  border: 1px solid var(--border);
  color: var(--text2);
  border-radius: 6px;
}

.minterms-section {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-size: 0.88rem;
  color: var(--text2);
}
.mono { font-family: monospace; color: var(--text); }

/* Animations */
.card { animation: fadeIn 0.3s ease; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }

/* ── Tabs ──────────────────────────────────────────────────────────────── */
.tab-strip {
  display: flex;
  gap: 4px;
  margin-bottom: -1px;
  position: relative;
  z-index: 1;
}
.tab {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 10px 22px;
  border-radius: 10px 10px 0 0;
  border: 1px solid var(--border);
  border-bottom: none;
  background: var(--surface2);
  color: var(--text2);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}
.tab:hover { background: var(--surface); color: var(--text); }
.tab.active {
  background: var(--surface);
  color: var(--text);
  border-color: var(--border);
}
.tab svg { opacity: 0.7; }
.tab.active svg { opacity: 1; }

.tab-pane {
  border-radius: 0 var(--radius) var(--radius) var(--radius);
}
.tab-pane.active { display: block; }

/* ── Circuit Builder ───────────────────────────────────────────────────── */
.circuit-layout {
  display: flex;
  gap: 0;
  height: 460px;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--border);
}

.gate-palette {
  width: 110px;
  min-width: 110px;
  background: #12142080;
  border-right: 1px solid var(--border);
  padding: 12px 8px;
  display: flex;
  flex-direction: column;
  gap: 5px;
  overflow-y: auto;
}
.palette-label {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--text2);
  text-transform: uppercase;
  padding: 2px 4px;
  margin-top: 4px;
}
.gate-palette-btn {
  width: 100%;
  padding: 7px 0;
  border-radius: 6px;
  border: 1.5px solid var(--gc, var(--border));
  background: transparent;
  color: var(--gc, var(--text));
  font-family: 'Consolas', monospace;
  font-size: 0.82rem;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.12s, transform 0.1s;
  text-align: center;
}
.gate-palette-btn:hover {
  background: color-mix(in srgb, var(--gc, var(--accent)) 15%, transparent);
  transform: translateX(2px);
  filter: none;
}
.palette-divider {
  height: 1px;
  background: var(--border);
  margin: 6px 0;
}
.palette-hint {
  font-size: 0.67rem;
  color: #555a7a;
  line-height: 1.4;
  padding: 0 2px;
}

.circuit-canvas-wrap {
  flex: 1;
  position: relative;
  overflow: hidden;
}
#circuit-canvas {
  display: block;
  width: 100%;
  height: 100%;
  cursor: crosshair;
}

.circuit-status {
  position: absolute;
  bottom: 8px;
  left: 50%;
  transform: translateX(-50%);
  background: #0b0d16cc;
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 3px 14px;
  font-size: 0.75rem;
  color: var(--text2);
  white-space: nowrap;
  pointer-events: none;
  backdrop-filter: blur(4px);
}

.circuit-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 14px;
  flex-wrap: wrap;
}
#analyze-circuit-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  background: linear-gradient(135deg, var(--accent), #8b5cf6);
  color: #fff;
}
.circuit-hint-text {
  font-size: 0.8rem;
  color: var(--text2);
  margin-left: auto;
}