body {
    background: radial-gradient(circle at top left, #1a1a2e, #16213e);
    color: #e9ecef;
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
}
.glass-panel {
    background: rgba(255, 255, 255, 0.05);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 1.5rem;
}
#canvasContainer {
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
    transition: transform 0.3s ease;
}
.custom-slider {
    accent-color: #4f46e5;
}
/* 隱藏原生 File Input */
#uploadInput { display: none; }

/* 載入中動畫 */
.loader {
    border: 3px solid rgba(255, 255, 255, 0.1);
    border-top: 3px solid #6366f1;
    border-radius: 50%;
    width: 20px;
    height: 20px;
    animation: spin 1s linear infinite;
    display: inline-block;
    vertical-align: middle;
    margin-right: 8px;
}
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }
#maskCanvas {
    transition: opacity 0.2s ease-in-out;
}