/* ========== RESET & BASE ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; overflow: hidden; }
body {
    font-family: 'Inter', sans-serif;
    background: #f0f2f7;
    color: #2d3748;
    font-size: 13px;
    line-height: 1.4;
}

/* ========== DASHBOARD GRID ========== */
#app {
    display: grid;
    grid-template-rows: auto 1fr auto;
    grid-template-columns: 260px 1fr 280px;
    grid-template-areas:
        "header header header"
        "controls tree sidebar"
        "status status status";
    height: 100vh;
    gap: 2px;
}

/* ========== HEADER ========== */
#header {
    grid-area: header;
    background: linear-gradient(135deg, #ffffff 0%, #f7f8fc 100%);
    padding: 10px 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid #dde1e8;
    box-shadow: 0 1px 3px rgba(0,0,0,0.06);
}
#header h1 {
    font-size: 20px;
    font-weight: 700;
    color: #1a202c;
}
#header .subtitle {
    font-size: 12px;
    color: #718096;
}

/* ========== PANELS ========== */
.panel {
    background: #ffffff;
    border: 1px solid #dde1e8;
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: #c4c9d4 #f5f6fa;
}
.panel::-webkit-scrollbar { width: 6px; }
.panel::-webkit-scrollbar-track { background: #f5f6fa; }
.panel::-webkit-scrollbar-thumb { background: #c4c9d4; border-radius: 3px; }
.panel-title {
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: #4a5568;
    padding: 12px 14px 6px;
    border-bottom: 1px solid #e8ecf1;
}

/* ========== CONTROLS PANEL ========== */
#controls {
    grid-area: controls;
    padding-bottom: 10px;
}
.control-group {
    padding: 8px 14px;
    border-bottom: 1px solid #eef0f5;
}
.control-group label {
    display: block;
    font-size: 11px;
    font-weight: 600;
    color: #4a5568;
    margin-bottom: 4px;
}
.control-group select,
.control-group input[type="number"] {
    width: 100%;
    background: #f7f8fc;
    border: 1px solid #cbd5e0;
    color: #2d3748;
    padding: 5px 8px;
    border-radius: 4px;
    font-size: 12px;
    font-family: 'Fira Code', monospace;
    outline: none;
}
.control-group select:focus,
.control-group input:focus {
    border-color: #0891b2;
    box-shadow: 0 0 0 3px rgba(8,145,178,0.15);
}
.slider-value {
    float: right;
    font-family: 'Fira Code', monospace;
    font-size: 11px;
    color: #0891b2;
}

/* ========== BUTTONS ========== */
.btn-group {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 6px;
    padding: 10px 14px;
}
.btn {
    padding: 7px 10px;
    border: 1px solid #cbd5e0;
    border-radius: 4px;
    background: #f7f8fc;
    color: #2d3748;
    font-size: 12px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    text-align: center;
}
.btn:hover { background: #edf0f5; border-color: #0891b2; }
.btn.primary { background: #ecfeff; border-color: #0891b2; color: #0891b2; }
.btn.primary:hover { background: #cffafe; }
.btn.danger { background: #fef2f2; border-color: #dc2626; color: #dc2626; }
.btn.danger:hover { background: #fee2e2; }
.btn:disabled { opacity: 0.4; cursor: not-allowed; }

/* ========== ITEMS TABLE ========== */
.items-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 11px;
    font-family: 'Fira Code', monospace;
}
.items-table th {
    background: #f7f8fc;
    color: #4a5568;
    padding: 4px 6px;
    text-align: center;
    font-weight: 600;
    font-size: 10px;
    text-transform: uppercase;
}
.items-table td {
    padding: 3px 6px;
    text-align: center;
    border-top: 1px solid #eef0f5;
}
.items-table tr:nth-child(even) { background: #f9fafb; }

/* ========== LEGEND ========== */
.legend-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 3px 14px;
    font-size: 11px;
}
.legend-dot {
    width: 10px; height: 10px;
    border-radius: 50%;
    flex-shrink: 0;
}

/* ========== TREE AREA ========== */
#tree-area {
    grid-area: tree;
    background: #f7f8fc;
    position: relative;
    overflow: hidden;
    border-left: 1px solid #dde1e8;
    border-right: 1px solid #dde1e8;
}
#tree-svg {
    width: 100%;
    height: 100%;
}

/* ========== SIDEBAR (PSEUDOCODE + VARIABLES) ========== */
#sidebar {
    grid-area: sidebar;
    display: flex;
    flex-direction: column;
}
#pseudocode-panel {
    flex: 1;
    min-height: 0;
}
#variables-panel {
    border-top: 2px solid #dde1e8;
    max-height: 340px;
}

/* ========== PSEUDOCODE ========== */
.pseudo-line {
    display: flex;
    align-items: flex-start;
    padding: 2px 10px 2px 6px;
    font-family: 'Fira Code', monospace;
    font-size: 11px;
    line-height: 1.5;
    transition: background 0.3s, border-color 0.3s;
    border-left: 3px solid transparent;
    white-space: pre;
}
.pseudo-line .line-num {
    color: #a0aec0;
    min-width: 22px;
    text-align: right;
    margin-right: 8px;
    font-size: 10px;
    user-select: none;
}
.pseudo-line.active {
    background: rgba(220, 38, 38, 0.08);
    border-left-color: #dc2626;
    color: #1a202c;
}
.pseudo-line .kw { color: #7c3aed; }
.pseudo-line .fn { color: #0891b2; }
.pseudo-line .cm { color: #a0aec0; }
.pseudo-line .op { color: #d97706; }
.pseudo-line .var { color: #1e293b; }

/* ========== VARIABLES PANEL ========== */
.var-row {
    display: flex;
    justify-content: space-between;
    padding: 4px 14px;
    font-family: 'Fira Code', monospace;
    font-size: 11px;
    border-bottom: 1px solid #eef0f5;
}
.var-label { color: #4a5568; }
.var-value { color: #0891b2; font-weight: 600; }
.var-value.green { color: #059669; }
.var-value.orange { color: #d97706; }
.var-value.red { color: #dc2626; }

/* ========== STATUS BAR ========== */
#status-bar {
    grid-area: status;
    background: #ffffff;
    border-top: 1px solid #dde1e8;
    padding: 8px 20px;
    font-size: 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: #718096;
    box-shadow: 0 -1px 3px rgba(0,0,0,0.04);
}
#status-bar .status-msg {
    color: #0891b2;
    font-weight: 600;
    font-size: 15px;
}

/* ========== SVG NODE STYLES ========== */
.node circle {
    fill: #ffffff;
    stroke: #94a3b8;
    stroke-width: 1.5;
    transition: fill 0.3s, stroke 0.3s;
}
.node text {
    fill: #475569;
    font-size: 9px;
    font-family: 'Fira Code', monospace;
}
/* radii set dynamically in JS based on n */
.link {
    fill: none;
    stroke: #cbd5e0;
    stroke-width: 1.5;
}
.link-label {
    fill: #64748b;
    font-size: 9px;
    font-family: 'Fira Code', monospace;
}

/* ========== HIGHLIGHT CLASSES ========== */
.node.highlight-current circle {
    stroke: #0891b2;
    stroke-width: 3;
    fill: #ecfeff;
    filter: url(#glow-cyan);
}
.node.highlight-best circle {
    stroke: #059669;
    stroke-width: 3;
    fill: #ecfdf5;
    filter: url(#glow-green);
}
.node.highlight-candidate circle {
    stroke: #d97706;
    stroke-width: 3;
    fill: #fffbeb;
    filter: url(#glow-orange);
}
.node.highlight-rejected circle {
    stroke: #dc2626;
    stroke-width: 3;
    fill: #fef2f2;
    filter: url(#glow-red);
}
.node.infeasible circle {
    fill: #fef2f2;
    stroke: #fca5a5;
    opacity: 0.6;
}
.node.infeasible text {
    opacity: 0.4;
}
.link.highlight-current {
    stroke: #0891b2;
    stroke-width: 2.5;
    filter: url(#glow-cyan);
}
.link.highlight-best {
    stroke: #059669;
    stroke-width: 2.5;
    filter: url(#glow-green);
}
.link.highlight-candidate {
    stroke: #d97706;
    stroke-width: 2;
    filter: url(#glow-orange);
}

/* ========== FLASH ANIMATION ========== */
@keyframes flash-reject {
    0% { stroke: #dc2626; stroke-width: 4; filter: url(#glow-red); }
    100% { stroke: #94a3b8; stroke-width: 1.5; filter: none; }
}
.node.flash-reject circle {
    animation: flash-reject 0.8s ease-out forwards;
}

/* ========== TOOLTIP ========== */
.node-tooltip {
    position: absolute;
    background: #ffffffee;
    border: 1px solid #dde1e8;
    border-radius: 6px;
    padding: 8px 12px;
    font-size: 11px;
    font-family: 'Fira Code', monospace;
    pointer-events: none;
    z-index: 100;
    display: none;
    max-width: 200px;
    box-shadow: 0 4px 16px rgba(0,0,0,0.1);
    color: #2d3748;
}