:root {
    --bg-page: #F8FAFC;
    --bg-surface: #FFFFFF;
    --border: #E2E8F0;
    
    --text-primary: #0F172A;
    --text-secondary: #475569;
    --text-tertiary: #94A3B8;
    
    --primary: #3B82F6;
    --primary-hover: #2563EB;
    
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05);
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-page);
    color: var(--text-primary);
    line-height: 1.5;
    height: 100vh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.hidden { display: none !important; }

/* Buttons & Inputs */
.btn {
    display: inline-flex; align-items: center; justify-content: center; gap: 8px;
    padding: 8px 16px; border-radius: var(--radius-sm);
    font-size: 14px; font-weight: 500; font-family: inherit;
    cursor: pointer; transition: all 0.2s; border: 1px solid transparent;
}
.btn-primary { background: var(--primary); color: white; }
.btn-primary:hover { background: var(--primary-hover); }
.btn-secondary { background: var(--bg-surface); border-color: var(--border); color: var(--text-primary); box-shadow: var(--shadow-sm); }
.btn-secondary:hover { background: #f1f5f9; }

.icon-btn {
    display: inline-flex; align-items: center; justify-content: center;
    width: 32px; height: 32px; border-radius: 6px; border: 1px solid var(--border);
    background: var(--bg-surface); color: var(--text-secondary); cursor: pointer; transition: all 0.2s;
}
.icon-btn:hover { background: #f1f5f9; color: var(--text-primary); }

/* Header */
.app-header {
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border);
    padding: 12px 24px; height: 64px;
    display: flex; justify-content: space-between; align-items: center;
    flex-shrink: 0; z-index: 10;
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--primary); }
.brand h1 { font-size: 18px; font-weight: 600; color: var(--text-primary); }

.header-actions { display: flex; align-items: center; gap: 12px; }

.color-count-control {
    display: flex; align-items: center; gap: 8px;
    font-size: 13px; font-weight: 500; color: var(--text-secondary);
    background: #f1f5f9; padding: 6px 12px; border-radius: 20px;
}
.color-count-control input[type="range"] {
    width: 80px; accent-color: var(--primary); cursor: pointer;
}
#color-count-val { font-variant-numeric: tabular-nums; width: 16px; text-align: right; }

.upload-btn-wrapper { position: relative; overflow: hidden; display: inline-block; }
.upload-btn-wrapper input[type=file] {
    font-size: 100px; position: absolute; left: 0; top: 0; opacity: 0; cursor: pointer; height: 100%;
}

/* Main Layout */
.app-container {
    flex-grow: 1; display: flex; overflow: hidden;
}

/* Left: Image Section */
.image-section {
    flex: 1.2;
    background: #e2e8f0;
    background-image: radial-gradient(#cbd5e1 1px, transparent 1px);
    background-size: 20px 20px;
    padding: 24px;
    display: flex; flex-direction: column;
    position: relative;
    border-right: 1px solid var(--border);
}

.dropzone {
    flex: 1; border: 2px dashed var(--border); border-radius: var(--radius-lg);
    background: rgba(255,255,255,0.8); backdrop-filter: blur(4px);
    display: flex; align-items: center; justify-content: center;
    transition: all 0.2s; position: relative; overflow: hidden;
}
.dropzone.empty-state { cursor: pointer; }
.dropzone.dragover { border-color: var(--primary); background: rgba(59, 130, 246, 0.05); }

.dropzone-content { text-align: center; color: var(--text-secondary); pointer-events: none; }
.drop-icon { color: var(--text-tertiary); margin-bottom: 16px; }
.dropzone-content h2 { font-size: 20px; font-weight: 600; color: var(--text-primary); margin-bottom: 8px; }
.dropzone-content p { font-size: 14px; }

.image-wrapper {
    position: absolute; top: 0; left: 0; right: 0; bottom: 0;
    display: flex; align-items: center; justify-content: center;
    padding: 16px; background: rgba(255,255,255,0.5);
}

.image-wrapper img {
    max-width: 100%; max-height: 100%; object-fit: contain;
    border-radius: var(--radius-md); box-shadow: var(--shadow-lg);
}

.loading-overlay {
    position: absolute; top:0; left:0; right:0; bottom:0;
    background: rgba(255,255,255,0.8); backdrop-filter: blur(4px);
    display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 16px;
    z-index: 10; font-weight: 500; color: var(--text-primary);
}

.spinner {
    width: 40px; height: 40px; border: 3px solid #e2e8f0;
    border-top-color: var(--primary); border-radius: 50%;
    animation: spin 1s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* Right: Palette Section */
.palette-section {
    flex: 1; max-width: 480px; min-width: 320px;
    background: var(--bg-surface);
    display: flex; flex-direction: column;
}

.palette-header {
    padding: 24px 24px 16px; display: flex; justify-content: space-between; align-items: center;
    border-bottom: 1px solid var(--border);
}
.palette-header h2 { font-size: 16px; font-weight: 600; }
.actions { display: flex; gap: 8px; }

.palette-empty {
    padding: 48px 24px; text-align: center; color: var(--text-tertiary); font-size: 14px;
}

/* Grid & Swatches */
.palette-grid {
    flex: 1; overflow-y: auto; padding: 24px;
    display: grid; grid-template-columns: repeat(auto-fill, minmax(100px, 1fr)); gap: 16px;
    align-content: start;
}

.swatch-card {
    background: var(--bg-page); border-radius: var(--radius-md); overflow: hidden;
    border: 1px solid var(--border); transition: transform 0.2s, box-shadow 0.2s;
    opacity: 0; transform: translateY(10px); animation: fadeUp 0.4s forwards;
    cursor: pointer; position: relative;
}
.swatch-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); border-color: #cbd5e1; }
.swatch-card:active { transform: translateY(0); }

@keyframes fadeUp { to { opacity: 1; transform: translateY(0); } }

.swatch-color { height: 80px; width: 100%; position: relative; }
.swatch-pct {
    position: absolute; top: 8px; right: 8px;
    background: rgba(0,0,0,0.5); color: white;
    font-size: 11px; font-weight: 600; padding: 2px 6px; border-radius: 10px;
}

.swatch-details { padding: 10px; display: flex; flex-direction: column; gap: 4px; }
.swatch-hex { font-weight: 600; font-size: 13px; color: var(--text-primary); text-transform: uppercase; }
.swatch-rgb { font-size: 11px; color: var(--text-secondary); font-variant-numeric: tabular-nums; }

/* Copy overlay */
.copy-overlay {
    position: absolute; top:0; left:0; right:0; bottom:0;
    background: rgba(255,255,255,0.9); display: flex; align-items: center; justify-content: center;
    font-size: 12px; font-weight: 600; color: var(--text-primary);
    opacity: 0; transition: opacity 0.2s; z-index: 5; pointer-events: none;
}
.swatch-card:active .copy-overlay { opacity: 1; }

/* Analytics */
.analytics {
    padding: 16px 24px; border-top: 1px solid var(--border); border-bottom: 1px solid var(--border);
    background: #f8fafc;
}
.analytics h3 { font-size: 12px; text-transform: uppercase; color: var(--text-tertiary); margin-bottom: 12px; font-weight: 600; letter-spacing: 0.5px; }

.analytics-card { background: white; border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 12px; }
.contrast-row { display: flex; justify-content: space-between; align-items: center; }
.contrast-row .label { font-size: 13px; font-weight: 500; }
.c-swatch {
    width: 60px; height: 30px; border-radius: var(--radius-sm); border: 1px solid rgba(0,0,0,0.1);
    display: flex; align-items: center; justify-content: center; font-weight: 600; font-size: 14px;
}

/* History */
.history-container {
    padding: 16px 24px 24px;
}
.history-container h3 { font-size: 12px; text-transform: uppercase; color: var(--text-tertiary); margin-bottom: 12px; font-weight: 600; letter-spacing: 0.5px; }

.history-track {
    display: flex; gap: 12px; overflow-x: auto; padding-bottom: 8px;
}
/* hide scrollbar */
.history-track::-webkit-scrollbar { height: 4px; }
.history-track::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 2px; }

.history-item {
    width: 60px; flex-shrink: 0; cursor: pointer; transition: opacity 0.2s;
}
.history-item:hover { opacity: 0.8; }
.h-img { width: 100%; height: 40px; border-radius: 4px; object-fit: cover; border: 1px solid var(--border); }
.h-palette { display: flex; height: 8px; border-radius: 2px; overflow: hidden; margin-top: 4px; }
.h-color { flex: 1; }

/* Toast */
.toast {
    position: fixed; bottom: -50px; left: 50%; transform: translateX(-50%);
    background: var(--text-primary); color: white;
    padding: 10px 20px; border-radius: 20px; font-size: 14px; font-weight: 500;
    opacity: 0; transition: all 0.3s; z-index: 1000; box-shadow: var(--shadow-md);
}
.toast.show { bottom: 24px; opacity: 1; }

/* Tooltips */
.tooltip { position: relative; }
.tooltip::after {
    content: attr(data-tooltip); position: absolute; bottom: 100%; left: 50%; transform: translateX(-50%) translateY(-4px);
    background: var(--text-primary); color: white; padding: 4px 8px; border-radius: 4px; font-size: 11px; font-weight: 500;
    white-space: nowrap; opacity: 0; pointer-events: none; transition: 0.2s; z-index: 100;
}
.tooltip:hover::after { opacity: 1; }