body {
    background-color: #0f172a;
    color: white;
    font-family: 'Segoe UI', system-ui, sans-serif;
    margin: 0;
    overflow: hidden;
    overscroll-behavior: none;
    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; justify-content: space-between;
    padding: 0 15px; z-index: 50; flex-shrink: 0;
}

.canvas-area {
    flex-grow: 1; position: relative; background: #0f172a; overflow: hidden;
}

canvas { display: block; width: 100%; height: 100%; }
canvas.interactive { cursor: pointer; }

/* 控制面板 */
.sandbox-controls {
    position: absolute; bottom: 20px; left: 50%;
    transform: translateX(-50%); background: rgba(15, 23, 42, 0.9);
    backdrop-filter: blur(8px); border: 1px solid rgba(255,255,255,0.2);
    padding: 10px 20px; border-radius: 16px;
    display: flex; gap: 15px; align-items: center; z-index: 45;
}

.icon-btn {
    display: flex; flex-direction: column; align-items: center; gap: 4px;
    background: transparent; border: none; color: white;
    cursor: pointer; padding: 8px 12px; border-radius: 8px; transition: background 0.2s;
}
.icon-btn:hover { background: rgba(255,255,255,0.1); }
.icon-btn:disabled { opacity: 0.3; cursor: not-allowed; }
.icon-btn span { font-size: 1.5rem; }
.icon-btn div { font-size: 0.75rem; color: #cbd5e1; }