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

html, body {
    width: 100%;
    height: 100%;
    background-color: #000;
    overflow: hidden;
}

canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: block;
}

/* 原理说明面板 */
.principle-panel {
    position: fixed;
    bottom: 20px;
    left: 20px;
    background: rgba(10, 10, 26, 0.85);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 12px;
    padding: 16px 20px;
    max-width: 420px;
    z-index: 50;
    font-size: 12px;
    line-height: 1.6;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.4);
    color: white;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    transition: all 0.3s ease;
}

.principle-title {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 12px;
    color: #a78bfa;
    letter-spacing: 0.5px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    user-select: none;
}

.principle-title:hover {
    color: #c4b5fd;
}

.toggle-icon {
    font-size: 10px;
    transition: transform 0.3s ease;
    display: inline-block;
}

.principle-panel:not(.collapsed) .toggle-icon {
    transform: rotate(90deg);
}

.principle-list {
    list-style: none;
    padding: 0;
    margin: 0;
    max-height: 300px;
    overflow: hidden;
    transition: max-height 0.3s ease, opacity 0.3s ease;
}

.principle-panel.collapsed .principle-list {
    max-height: 0;
    opacity: 0;
}

.principle-panel.collapsed .principle-title {
    margin-bottom: 0;
}

.principle-list li {
    padding: 6px 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    color: rgba(255, 255, 255, 0.85);
}

.principle-list li:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.principle-list li strong {
    color: #60a5fa;
    font-weight: 500;
}

/* 响应式 */
@media (max-width: 768px) {
    .principle-panel {
        left: 10px;
        right: 10px;
        bottom: 10px;
        max-width: none;
    }
}