:root {
    --bg: #0c0c0f;
    --surface: #16161a;
    --surface-alt: #1e1e24;
    --border: #2a2a32;
    --accent: #6366f1;
    --accent-hover: #818cf8;
    --success: #22c55e;
    --error: #ef4444;
    --text: #f4f4f5;
    --text-muted: #a1a1aa;
}
* { box-sizing: border-box; }
body {
    font-family: 'Outfit', sans-serif;
    font-size: 16px;
    margin: 0;
    padding: 2rem;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
}
.container { max-width: 960px; margin: 0 auto; }

header {
    text-align: center;
    margin-bottom: 2.5rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--border);
}
header h1 {
    margin: 0;
    font-size: 2rem;
    font-weight: 700;
    letter-spacing: -0.03em;
    background: linear-gradient(135deg, #fff 40%, var(--text-muted));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
header p {
    margin: 0.75rem 0 0;
    color: var(--text-muted);
    font-size: 1rem;
}

.formula-intro, .formula {
    color: var(--text-muted);
    font-size: 0.95rem;
    margin-bottom: 0.75rem;
}
.katex { font-size: 1em !important; }

.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    margin-bottom: 1.5rem;
    overflow: hidden;
}
.card.accordion-item {
    padding: 0;
}
.card.accordion-item .accordion-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.5rem;
    cursor: pointer;
    user-select: none;
    transition: background 0.2s;
}
.card.accordion-item .accordion-header:hover {
    background: var(--surface-alt);
}
.card.accordion-item .accordion-header h2 {
    margin: 0;
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--text);
}
.card.accordion-item .accordion-icon {
    font-size: 0.8rem;
    color: var(--text-muted);
    transition: transform 0.2s;
}
.card.accordion-item .accordion-content {
    padding: 0 1.5rem 1.5rem;
    overflow: hidden;
    transition: max-height 0.3s ease-out, opacity 0.2s;
}
.card.accordion-item.collapsed .accordion-content {
    max-height: 0;
    padding-top: 0;
    padding-bottom: 0;
    opacity: 0;
}
.card.accordion-item:not(.collapsed) .accordion-content {
    max-height: 2000px;
}
.card.accordion-item.collapsed .accordion-icon {
    transform: rotate(-90deg);
}
.card:not(.accordion-item) h2 {
    margin: 0 0 1rem;
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--text);
}
.card:not(.accordion-item) {
    padding: 1.5rem;
}

.control-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem 1.5rem;
    align-items: center;
    margin-bottom: 0.75rem;
}
.control-row label { color: var(--text-muted); font-size: 0.9rem; }
.control-row input[type="text"],
.control-row input[type="number"] {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.95rem;
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--surface-alt);
    color: var(--text);
    width: 120px;
}
.control-row input:focus {
    outline: none;
    border-color: var(--accent);
}

.btn-primary, .btn-secondary {
    font-family: 'Outfit', sans-serif;
    font-size: 1rem;
    font-weight: 600;
    padding: 0.65rem 1.25rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.2s;
}
.btn-primary {
    background: var(--accent);
    color: white;
}
.btn-primary:hover { background: var(--accent-hover); }
.btn-secondary {
    background: var(--surface-alt);
    color: var(--text);
    border: 1px solid var(--border);
}
.btn-secondary:hover { background: var(--border); }
button:disabled { opacity: 0.5; cursor: not-allowed; }

.canvas-wrapper {
    display: flex;
    justify-content: center;
    background: var(--surface-alt);
    border-radius: 8px;
    padding: 0.75rem;
    margin-bottom: 1rem;
}
.canvas-wrapper canvas {
    border-radius: 6px;
    display: block;
}

.output-box, .contributors-list, .beacon-result {
    margin-top: 1rem;
    padding: 1rem;
    border-radius: 8px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9rem;
}
.output-box {
    background: var(--surface-alt);
    border: 1px solid var(--border);
    color: var(--text);
    white-space: pre-wrap;
}
.beacon-result {
    background: rgba(34, 197, 94, 0.15);
    border: 1px solid var(--success);
    color: var(--success);
    font-weight: 600;
}
.muted { color: var(--text-muted); }

.nodes-list { margin: 1rem 0; }
.node-msg {
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
    min-height: 1.4em;
}
.node-item {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem 1rem;
    align-items: center;
    padding: 0.75rem;
    margin-bottom: 0.5rem;
    background: var(--surface-alt);
    border-radius: 8px;
    border: 1px solid var(--border);
}
.node-item .node-pk { font-family: 'JetBrains Mono', monospace; font-size: 0.85rem; }
.node-item .remove-node,
.node-item .reselect-node {
    padding: 0.25rem 0.5rem;
    font-size: 0.85rem;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}
.node-item .remove-node {
    background: var(--error);
    color: white;
}
.node-item .reselect-node {
    background: var(--surface);
    color: var(--accent);
    border: 1px solid var(--accent);
}
.node-item .reselect-node:hover { background: rgba(99, 102, 241, 0.2); }
.eligible { color: var(--success); }
.not-eligible { color: var(--error); }

/* Step 3: Contrib layout */
.step3-layout,
.contrib-step3-layout {
    display: flex;
    gap: 1.5rem;
    margin: 1rem 0;
    align-items: flex-start;
}
.contrib-eligible-list {
    flex-shrink: 0;
    width: 180px;
    background: var(--surface-alt);
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
}
.contrib-list-label {
    padding: 0.5rem 0.75rem;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border);
}
.contrib-eligible-nodes {
    max-height: 200px;
    overflow-y: auto;
}
.contrib-node-chip {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.6rem 0.75rem;
    font-size: 0.9rem;
    cursor: pointer;
    border-bottom: 1px solid var(--border);
    transition: background 0.2s;
}
.contrib-node-chip:last-child { border-bottom: none; }
.contrib-node-chip:hover {
    background: var(--surface);
}
.contrib-node-chip.selected {
    background: rgba(99, 102, 241, 0.2);
    border-left: 3px solid var(--accent);
}
.contrib-node-chip.contributed .contrib-node-tick {
    color: var(--success);
}
.contrib-node-tick {
    font-size: 1rem;
    color: var(--text-muted);
}
.contrib-controls-panel {
    flex: 1;
    min-width: 0;
    background: var(--surface-alt);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1rem;
}
.contrib-placeholder {
    font-size: 0.9rem;
}
.contrib-controls .control-row {
    margin-bottom: 0.5rem;
}