/* ── Electro-Pneumatic Circuit Simulator ────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:        #0d1117;
  --surface:   #161b27;
  --surface2:  #1f2535;
  --border:    #2a3050;
  --accent:    #ff9800;
  --accent-lo: rgba(255,152,0,.22);
  --green:     #3ddc84;
  --red:       #ff5555;
  --gold:      #f5c842;
  --blue:      #42a5f5;
  --text:      #dde3f0;
  --text-dim:  #6b7a99;
  --font:      'Segoe UI', system-ui, sans-serif;
  --mono:      'Courier New', monospace;
  --radius:    12px;
}

body { background: var(--bg); color: var(--text); font-family: var(--font); min-height: 100vh; padding: 0 16px; }
#app { max-width: 1140px; margin: 0 auto; display: flex; flex-direction: column; gap: 14px; }

/* ── Header ──────────────────────────────────────────────────── */
header { text-align: center; padding: 4px 0; }
header h1 {
  font-size: 1.8rem; font-weight: 700;
  background: linear-gradient(120deg, #ff9800 0%, #ffcc80 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.subtitle { color: var(--text-dim); font-size: 0.85rem; margin-top: 3px; }

/* ── Controls bar ────────────────────────────────────────────── */
.controls-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 14px;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.ctrl-group { display: flex; align-items: center; gap: 8px; }
.ctrl-label { font-size: 0.72rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-dim); white-space: nowrap; }

.pill-tabs { display: flex; background: var(--bg); border-radius: 8px; padding: 3px; gap: 2px; flex-wrap: wrap; }
.pill {
  padding: 5px 13px; border: none; background: transparent; color: var(--text-dim);
  border-radius: 6px; cursor: pointer; font-size: 0.81rem;
  transition: background .18s, color .18s, box-shadow .18s;
}
.pill.active { background: var(--accent); color: #fff; box-shadow: 0 0 12px var(--accent-lo); }
.pill:hover:not(.active) { background: var(--surface2); color: var(--text); }

/* ── Buttons ─────────────────────────────────────────────────── */
.btn {
  padding: 8px 18px; border: none; border-radius: 8px; cursor: pointer;
  font-size: 0.84rem; font-weight: 600; transition: filter .18s, box-shadow .18s, opacity .18s;
}
.btn:disabled { opacity: 0.38; cursor: not-allowed; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:not(:disabled):hover { filter: brightness(1.12); box-shadow: 0 0 12px var(--accent-lo); }
.btn-ghost { background: var(--surface2); color: var(--text); border: 1px solid var(--border); }
.btn-ghost:hover { background: var(--border); }

/* ── User Guide button ───────────────────────────────────────── */
.btn-guide {
  margin-left: auto;
  padding: 6px 16px; border: none; border-radius: 8px; cursor: pointer;
  font-size: 0.82rem; font-weight: 700;
  background: var(--gold); color: #1a1a2e;
  transition: filter .18s, box-shadow .18s;
}
.btn-guide:hover { filter: brightness(1.1); box-shadow: 0 0 14px rgba(245,200,66,.35); }

/* ── Builder layout ──────────────────────────────────────────── */
.builder-layout { display: flex; gap: 12px; min-height: 480px; }
.canvas-area { flex: 1; display: flex; flex-direction: column; gap: 8px; min-width: 0; }

/* ── Component palette — collapsible categories ─────────────── */
.component-palette {
  width: 200px; flex-shrink: 0; align-self: flex-start;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 8px 6px; display: flex; flex-direction: column; gap: 2px;
  overflow-y: auto; max-height: 520px;
}
.palette-title {
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-dim); text-align: center; padding-bottom: 6px;
  border-bottom: 1px solid var(--border); margin-bottom: 4px;
}

/* ── Collapsible category header ── */
.palette-cat {
  display: flex; align-items: center; justify-content: space-between;
  padding: 5px 6px; margin-top: 2px; border-radius: 6px;
  cursor: pointer; user-select: none;
  font-size: 0.7rem; font-weight: 700; text-transform: uppercase; letter-spacing: .04em;
  color: var(--blue); transition: background .15s;
}
.palette-cat:hover { background: var(--surface2); }
/* ── Electrical category accent ── */
.palette-cat[data-cat="electrical"] { color: #ff9800; }
.palette-cat .cat-arrow {
  font-size: 0.6rem; transition: transform .2s; display: inline-block;
}
.palette-cat.collapsed .cat-arrow { transform: rotate(-90deg); }
.palette-cat-items {
  display: flex; flex-direction: column; gap: 1px;
  overflow: hidden; transition: max-height .25s ease;
  max-height: 600px; flex-shrink: 0;
}
.palette-cat.collapsed + .palette-cat-items {
  max-height: 0;
}

.palette-item {
  display: flex; align-items: center; gap: 6px; padding: 4px 6px;
  border-radius: 6px; cursor: grab; transition: background .15s;
  font-size: 0.7rem; color: var(--text-dim);
}
.palette-item:hover { background: var(--surface2); color: var(--text); }
.palette-item:active { cursor: grabbing; }
.palette-icon { flex-shrink: 0; border-radius: 4px; }

/* ── Canvas card ─────────────────────────────────────────────── */
.canvas-card {
  width: 100%; background: #0a0e14;
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 0; position: relative; overflow-x: clip; flex: 1;
}
.canvas-card canvas { display: block; width: 100%; height: 100%; min-height: 420px; cursor: crosshair; touch-action: none; }

/* ── Canvas toolbar ──────────────────────────────────────────── */
.canvas-toolbar {
  display: flex; align-items: center; gap: 8px; flex-wrap: wrap;
  padding: 8px 12px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.toolbar-hint { flex: 1; font-size: 0.72rem; color: var(--text-dim); text-align: right; }

/* ── Domain legend ── */
.domain-legend {
  display: flex; align-items: center; gap: 16px; justify-content: center;
  padding: 6px 12px; font-size: 0.72rem; color: var(--text-dim);
}
.domain-legend-dot {
  display: inline-block; width: 10px; height: 10px; border-radius: 50%;
  margin-right: 4px; vertical-align: middle;
}
.domain-legend-sq {
  display: inline-block; width: 8px; height: 8px; border-radius: 2px;
  margin-right: 4px; vertical-align: middle;
}

/* ── Properties panel ────────────────────────────────────────── */
.properties-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px;
}
.props-title {
  font-size: 0.75rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-dim); margin-bottom: 10px; border-bottom: 1px solid var(--border); padding-bottom: 6px;
}
.props-body label {
  display: flex; flex-direction: column; gap: 3px; margin-bottom: 8px;
  font-size: 0.78rem; color: var(--text-dim);
}
.props-body input[type="range"] { width: 100%; accent-color: var(--accent); }
.props-body select {
  padding: 5px 8px; border-radius: 6px; border: 1px solid var(--border);
  background: var(--bg); color: var(--text); font-size: 0.82rem;
}
.props-body .prop-val { font-weight: 600; color: var(--text); font-size: 0.85rem; }

/* ── Readouts ────────────────────────────────────────────────── */
.readout-row {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); gap: 10px;
}
.readout-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 10px 14px; text-align: center;
}
.readout-label { font-size: 0.68rem; color: var(--text-dim); text-transform: uppercase; letter-spacing: .05em; margin-bottom: 4px; }
.readout-val { font-size: 1.25rem; font-weight: 700; color: var(--accent); }
.readout-unit { font-size: 0.75rem; color: var(--text-dim); margin-left: 2px; }

/* ── Warning bar ─────────────────────────────────────────────── */
.warning-bar {
  padding: 8px 14px; border-radius: 8px; font-size: 0.82rem; font-weight: 600;
  background: rgba(255,85,85,.12); color: var(--red); border: 1px solid rgba(255,85,85,.3);
}

/* ── Circuit description ─────────────────────────────────────── */
.circuit-desc {
  padding: 10px 16px; border-radius: 8px; font-size: 0.82rem;
  background: var(--surface); border: 1px solid var(--border); color: var(--text-dim);
  line-height: 1.5;
}

/* ── Explore mode ────────────────────────────────────────────── */
.item-selector {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px;
}
.is-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 8px; margin-top: 8px; }
.is-card {
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px; cursor: pointer; transition: border-color .15s, background .15s;
}
.is-card:hover { border-color: var(--accent); background: var(--surface2); }
.is-card.active { border-color: var(--accent); background: var(--accent-lo); }
.is-card-name { font-size: 0.82rem; font-weight: 600; color: var(--text); }
.is-card-symbol { font-size: 0.7rem; color: var(--text-dim); margin-top: 2px; }

.item-info {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px; line-height: 1.6;
}
.item-info h3 { font-size: 1.1rem; color: var(--accent); margin-bottom: 8px; }
.item-info h4 { font-size: 0.9rem; color: var(--blue); margin: 12px 0 4px; }
.item-info p { font-size: 0.85rem; color: var(--text-dim); margin-bottom: 8px; }
.item-info ul, .item-info ol { font-size: 0.83rem; color: var(--text-dim); padding-left: 20px; margin-bottom: 8px; }
.item-info li { margin-bottom: 3px; }
.item-info .formula-box {
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px 14px; font-family: var(--mono); font-size: 0.85rem; color: var(--gold); margin: 8px 0;
}
.item-info .example-box {
  background: rgba(255,152,0,.06); border: 1px solid rgba(255,152,0,.2); border-radius: 8px;
  padding: 10px 14px; margin-top: 10px;
}
.item-info .example-box .step { font-size: 0.82rem; color: var(--text-dim); font-family: var(--mono); }

/* ── Practice mode ───────────────────────────────────────────── */
.practice-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px;
}
.pp-prompt { font-size: 0.95rem; line-height: 1.5; margin-bottom: 14px; }
.pp-input-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.pp-input {
  width: 120px; padding: 8px 12px; border-radius: 8px; border: 1px solid var(--border);
  background: var(--bg); color: var(--text); font-size: 1rem;
}
.pp-unit { font-size: 0.85rem; color: var(--text-dim); }
.pp-bottom { margin-top: 12px; }
.feedback { font-weight: 600; font-size: 0.9rem; }
.feedback.correct { color: var(--green); }
.feedback.wrong { color: var(--red); }
.solution-panel {
  margin-top: 12px; padding: 12px 14px; border-radius: 8px;
  background: var(--bg); border: 1px solid var(--border);
  font-size: 0.85rem; line-height: 1.6; color: var(--text-dim);
}
.practice-bar {
  display: flex; align-items: center; gap: 14px;
  padding: 10px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.pbar-score { font-size: 0.85rem; color: var(--accent); font-weight: 600; }

/* ── Quiz mode ───────────────────────────────────────────────── */
.question-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px;
}
.q-prompt { font-size: 0.95rem; line-height: 1.5; margin-bottom: 14px; }
.q-options { display: flex; flex-direction: column; gap: 8px; }
.q-opt {
  padding: 10px 14px; border-radius: 8px; cursor: pointer;
  background: var(--bg); border: 1px solid var(--border);
  font-size: 0.88rem; transition: border-color .15s, background .15s;
}
.q-opt:hover { border-color: var(--accent); background: var(--surface2); }
.q-opt.selected { border-color: var(--accent); background: var(--accent-lo); }
.q-opt.correct { border-color: var(--green); background: rgba(61,220,132,.12); color: var(--green); }
.q-opt.wrong { border-color: var(--red); background: rgba(255,85,85,.12); color: var(--red); }
.q-num-input {
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
}
.q-num-input input {
  width: 120px; padding: 8px 12px; border-radius: 8px; border: 1px solid var(--border);
  background: var(--bg); color: var(--text); font-size: 1rem;
}
.quiz-bar {
  display: flex; align-items: center; gap: 14px;
  padding: 10px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.qbar-counter { display: flex; align-items: baseline; gap: 4px; }
.qbar-q-label { font-size: 0.7rem; color: var(--text-dim); text-transform: uppercase; }
.qbar-q-num { font-size: 1.2rem; font-weight: 700; color: var(--accent); }
.qbar-q-sep { color: var(--text-dim); }
.qbar-q-total { font-size: 0.9rem; color: var(--text-dim); }
.quiz-result {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px; text-align: center;
}
.quiz-result h3 { font-size: 1.3rem; color: var(--accent); margin-bottom: 8px; }
.quiz-result .score { font-size: 2rem; font-weight: 700; color: var(--gold); }

/* ── User Guide Modal ────────────────────────────────────────── */
.guide-overlay {
  position: fixed; inset: 0; z-index: 1000;
  background: rgba(0,0,0,.65); display: flex; align-items: center; justify-content: center;
}
.guide-modal {
  background: var(--surface); border: 1px solid var(--border); border-radius: 16px;
  max-width: 780px; width: 92%; max-height: 85vh;
  display: flex; flex-direction: column; box-shadow: 0 12px 48px rgba(0,0,0,.6);
}
.guide-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 24px; border-bottom: 1px solid var(--border);
}
.guide-header h2 { font-size: 1.15rem; color: var(--accent); }
.guide-close {
  background: none; border: none; color: var(--text-dim); font-size: 1.6rem;
  cursor: pointer; padding: 4px 8px; border-radius: 6px; transition: color .15s, background .15s;
}
.guide-close:hover { color: var(--red); background: rgba(255,85,85,.12); }
.guide-body {
  overflow-y: auto; padding: 20px 24px; flex: 1;
}
.guide-body h3 { color: var(--accent); font-size: 1rem; margin: 18px 0 8px; padding-bottom: 4px; border-bottom: 1px solid var(--border); }
.guide-body h3:first-child { margin-top: 0; }
.guide-body h4 { color: var(--blue); font-size: 0.88rem; margin: 12px 0 4px; }
.guide-body p { font-size: 0.84rem; color: var(--text-dim); line-height: 1.6; margin-bottom: 8px; }
.guide-body ul, .guide-body ol { font-size: 0.83rem; color: var(--text-dim); padding-left: 20px; margin-bottom: 8px; line-height: 1.5; }
.guide-body li { margin-bottom: 3px; }
.guide-body kbd {
  display: inline-block; padding: 1px 6px; border-radius: 4px;
  background: var(--bg); border: 1px solid var(--border); font-family: var(--mono);
  font-size: 0.78rem; color: var(--text);
}
.guide-body table { width: 100%; border-collapse: collapse; margin: 8px 0 12px; font-size: 0.82rem; }
.guide-body th { text-align: left; padding: 6px 10px; border-bottom: 2px solid var(--border); color: var(--text); font-weight: 600; }
.guide-body td { padding: 5px 10px; border-bottom: 1px solid var(--border); color: var(--text-dim); }
.guide-body strong { color: var(--text); }

/* ── Context menu ────────────────────────────────────────────── */
.ctx-item:hover { background: var(--surface2); }

/* ── SEO article ─────────────────────────────────────────────── */
.seo-article {
  padding: 28px 24px; line-height: 1.75;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.seo-article h2 { font-size: 1.3rem; color: var(--text); margin-bottom: 12px; }
.seo-article h3 { font-size: 1.05rem; color: var(--accent); margin: 18px 0 6px; }
.seo-article p { font-size: 0.92rem; color: var(--text-dim); margin-bottom: 10px; }
.seo-article a { color: var(--accent); text-decoration: underline; }
.seo-article a:hover { color: #ffb74d; }

/* ── Responsive ──────────────────────────────────────────────── */
@media (max-width: 768px) {
  .builder-layout { flex-direction: column; }
  .component-palette { width: 100%; max-height: 180px; flex-direction: row; flex-wrap: wrap; gap: 4px; overflow-x: auto; }
  .palette-cat-items { flex-direction: row; flex-wrap: wrap; }
  .readout-row { grid-template-columns: repeat(3, 1fr); }
  .guide-modal { width: 95%; max-height: 90vh; }
  .guide-header { padding: 14px 18px; }
  .guide-body { padding: 14px 18px; }
}

@media (max-width: 500px) {
  header h1 { font-size: 1.3rem; }
  .controls-bar { padding: 8px 10px; gap: 8px; }
  .pill { padding: 4px 10px; font-size: 0.75rem; }
  .component-palette { max-height: 140px; }
  .readout-row { grid-template-columns: repeat(2, 1fr); }
  .guide-modal { width: 100%; max-height: 100vh; border-radius: 0; }
  .guide-header h2 { font-size: 0.95rem; }
  .guide-body { padding: 12px 14px; }
}