body {
    background-color: #0f172a;
    color: white;
    font-family: 'PingFang TC', 'Microsoft JhengHei', system-ui, sans-serif;
    margin: 0;
    overflow: hidden;
    touch-action: none;
    user-select: none;
}

#app {
    position: fixed;
    top: 0; left: 0;
    width: 100vw; height: 100dvh;
    display: flex; flex-direction: column;
}

.top-bar {
    height: 50px;
    background: #1e293b;
    border-bottom: 1px solid #334155;
    display: flex; align-items: center;
    padding: 0 15px;
    z-index: 100;
}

.canvas-area {
    flex-grow: 1;
    position: relative;
    background: #020617;
}

/* 層級 1: 畫布 */
canvas {
    position: absolute;
    top: 0; left: 0;
    z-index: 1;
}

/* 層級 10: 選單 (無底框) */
.media-menu {
    position: absolute;
    top: 52%; /* 中間線下方 */
    left: 24px;
    z-index: 50;
}

/* 層級 20: 光源 (最高層) */
.source-handle {
    position: absolute;
    width: 50px; /* 大感應區 */
    height: 50px;
    transform: translate(-50%, -50%);
    z-index: 100; /* 最高圖層 */
    cursor: grab;
    display: flex;
    align-items: center;
    justify-content: center;
}

.source-handle:active { cursor: grabbing; }

.handle-core {
    width: 26px; /* 恢復較大的圈圈 */
    height: 26px;
    background: #facc15;
    border: 4px solid white;
    border-radius: 50%;
    box-shadow: 0 0 20px rgba(250, 204, 21, 0.8), 0 0 40px rgba(250, 204, 21, 0.4);
}