/* ========================================
   2D Convolution & Kernel Inspection
   ======================================== */

:root {
    --bg-primary: #0c0e14;
    --bg-secondary: #14171f;
    --bg-surface: #1a1e2a;
    --bg-elevated: #222738;
    --border: #2e3448;
    --border-bright: #3d4560;
    --text-primary: #e8ecf4;
    --text-secondary: #9da5b8;
    --text-muted: #6b7280;
    --accent: #6c8cff;
    --accent-glow: rgba(108, 140, 255, 0.25);
    --accent-bright: #8baafe;
    --positive: #4ade80;
    --negative: #f87171;
    --warning: #fbbf24;
    --pixel-hi: #f59e0b;
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --transition: 180ms ease;
    --panel-header-h: 0;
}

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

html {
    font-size: 15px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-primary);
    color: var(--text-primary);
    overflow-x: hidden;
    min-height: 100dvh;
}

/* Remove default number-input spinners */
input[type=number]::-webkit-inner-spin-button,
input[type=number]::-webkit-outer-spin-button {
    -webkit-appearance: none; margin: 0;
}
input[type=number] { -moz-appearance: textfield; }

/* ── Back Button ──────────────────────── */
#back-btn {
    position: fixed;
    top: 12px;
    right: 16px;
    z-index: 1000;
    background: var(--bg-elevated);
    color: var(--text-primary);
    border: 1px solid var(--border-bright);
    padding: 8px 18px;
    font-family: var(--font-sans);
    font-size: 0.85rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background var(--transition), border-color var(--transition);
    backdrop-filter: blur(8px);
}
#back-btn:hover {
    background: var(--accent);
    border-color: var(--accent);
    color: #fff;
}

/* ── Control Panel (Fixed Top) ────────── */
#control-panel {
    position: fixed;
    top: 0; left: 0; right: 0;
    z-index: 900;
    background: linear-gradient(180deg, var(--bg-secondary) 80%, transparent);
    backdrop-filter: blur(14px);
    padding: 14px 24px 18px;
    border-bottom: 1px solid var(--border);
}
#control-panel h1 {
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--accent-bright);
    letter-spacing: -0.02em;
    margin-bottom: 10px;
}

.controls-row {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    align-items: flex-end;
}
.control-group {
    display: flex;
    flex-direction: column;
    gap: 4px;
}
.control-group label {
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-secondary);
}
.control-group select,
.control-group input {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    background: var(--bg-elevated);
    color: var(--text-primary);
    border: 1px solid var(--border);
    padding: 7px 12px;
    border-radius: var(--radius-sm);
    outline: none;
    transition: border-color var(--transition);
    min-width: 140px;
}
.control-group select:focus,
.control-group input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

/* Custom Kernel Section */
#custom-kernel-section {
    margin-top: 10px;
}
#custom-kernel-section label {
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-secondary);
    display: block;
    margin-bottom: 6px;
}
#custom-kernel-grid {
    display: grid;
    grid-template-columns: repeat(3, 64px);
    gap: 4px;
}
#custom-kernel-grid input {
    width: 64px;
    height: 36px;
    text-align: center;
    font-family: var(--font-mono);
    font-size: 0.82rem;
    background: var(--bg-elevated);
    color: var(--text-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    outline: none;
    transition: border-color var(--transition);
}
#custom-kernel-grid input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}
.hidden { display: none !important; }

/* ── Main Content Layout ──────────────── */
#main-content {
    display: flex;
    padding-top: var(--panel-header-h);
    min-height: 100dvh;
}

/* Image Area */
#image-area {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    overflow: hidden;
    position: relative;
}

#canvas-container {
    position: relative;
    display: inline-block;
    border: 2px solid var(--border);
    border-radius: var(--radius-md);
    overflow: hidden;
    touch-action: none;
    cursor: crosshair;
    background: #000;
}

#source-canvas {
    display: block;
    image-rendering: pixelated;
    -ms-interpolation-mode: nearest-neighbor;
}

/* Crosshair marker */
#crosshair {
    position: absolute;
    width: 48px;
    height: 48px;
    pointer-events: auto;
    touch-action: none;
    cursor: grab;
    z-index: 10;
    transform: translate(-50%, -50%);
    transition: none;
}
#crosshair:active { cursor: grabbing; }

.crosshair-ring {
    position: absolute;
    top: 50%; left: 50%;
    width: 32px; height: 32px;
    transform: translate(-50%, -50%);
    border: 2.5px solid var(--accent-bright);
    border-radius: 50%;
    box-shadow: 0 0 12px var(--accent-glow), inset 0 0 6px var(--accent-glow);
    animation: pulse-ring 2s ease-in-out infinite;
}
@keyframes pulse-ring {
    0%, 100% { box-shadow: 0 0 8px var(--accent-glow), inset 0 0 4px var(--accent-glow); }
    50% { box-shadow: 0 0 18px var(--accent-glow), inset 0 0 10px var(--accent-glow); }
}
.crosshair-h, .crosshair-v {
    position: absolute;
    background: var(--accent-bright);
    opacity: 0.7;
}
.crosshair-h { top: 50%; left: 0; right: 0; height: 1.5px; transform: translateY(-50%); }
.crosshair-v { left: 50%; top: 0; bottom: 0; width: 1.5px; transform: translateX(-50%); }

/* Neighborhood box overlay */
#neighborhood-box {
    position: absolute;
    border: 2px solid var(--warning);
    box-shadow: 0 0 10px rgba(251, 191, 36, 0.35);
    pointer-events: none;
    z-index: 5;
    border-radius: 2px;
}

/* ── Detail Panel ─────────────────────── */
#detail-panel {
    width: 380px;
    min-width: 320px;
    background: var(--bg-secondary);
    border-left: 1px solid var(--border);
    padding: 20px 22px 30px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 22px;
}
#detail-panel h2 {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--accent-bright);
    letter-spacing: -0.01em;
}
#detail-panel h3 {
    font-size: 0.72rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

/* Inspector grids */
.inspector-grids {
    display: flex;
    gap: 18px;
    flex-wrap: wrap;
}
.grid-section {
    flex: 1;
    min-width: 140px;
}
.value-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 3px;
}
.value-grid .cell {
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    text-align: center;
    padding: 8px 4px;
    font-family: var(--font-mono);
    font-size: 0.78rem;
    font-weight: 500;
    color: var(--text-primary);
    transition: background var(--transition), border-color var(--transition);
}
.value-grid .cell.highlight {
    border-color: var(--accent);
    background: rgba(108, 140, 255, 0.12);
}
.value-grid .cell.positive { color: var(--positive); }
.value-grid .cell.negative { color: var(--negative); }
.value-grid .cell.zero { color: var(--text-muted); }

/* Calculation display */
.calculation-section {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 14px 16px;
}
#calculation-display {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    line-height: 1.7;
    color: var(--text-secondary);
    word-break: break-all;
    max-height: 120px;
    overflow-y: auto;
}
#result-value {
    margin-top: 10px;
    font-family: var(--font-mono);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--accent-bright);
    text-align: center;
    padding: 8px;
    border-top: 1px solid var(--border);
}

/* Output canvas */
.output-section {
    text-align: center;
}
#output-canvas {
    display: block;
    margin: 0 auto;
    image-rendering: pixelated;
    -ms-interpolation-mode: nearest-neighbor;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    background: #000;
    max-width: 100%;
}

/* ── Responsive ───────────────────────── */
@media (max-width: 860px) {
    #main-content {
        flex-direction: column;
    }
    #detail-panel {
        width: 100%;
        min-width: unset;
        border-left: none;
        border-top: 1px solid var(--border);
    }
    #image-area {
        min-height: 300px;
    }
    #control-panel {
        padding: 10px 14px 14px;
    }
    #control-panel h1 {
        font-size: 0.9rem;
    }
    .controls-row {
        gap: 10px;
    }
    .control-group select {
        min-width: 110px;
    }
    #custom-kernel-grid {
        grid-template-columns: repeat(3, 56px);
    }
    #custom-kernel-grid input {
        width: 56px;
        height: 32px;
    }
    #back-btn {
        padding: 6px 14px;
        font-size: 0.8rem;
    }
}

@media (max-width: 480px) {
    .inspector-grids {
        flex-direction: column;
        gap: 14px;
    }
}

/* Scrollbar styling */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border-bright); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }