:root {
    --bg-color: #1a1a1a;
    --canvas-bg-color: #2a2a2e;
    --node-bg-color: #4a4a52;
    --node-border-color: #8c8c9a;
    --text-color: #f0f0f0;
    --accent-color: #00aaff;
    --connection-color: #888;
    --grid-color: rgba(255, 255, 255, 0.1); /* White grid for dark theme */
    --connection-highlight-color: var(--accent-color);
    --selection-color: rgba(0, 170, 255, 0.3);
    --multi-selection-color: rgba(255, 193, 7, 0.3);
}

/* Light Theme */
html.light-theme {
    --bg-color: #f0f2f5;
    --canvas-bg-color: #611e1e00;
    --node-bg-color: #e9ecef;
    --node-border-color: #ced4da;
    --text-color: #343a40;
    --connection-color: #adb5bd;
    --grid-color: rgba(0, 0, 0, 0.08); /* Gray grid for light theme */
}

/* Light No Grid Theme */
html.light-nogrid-theme {
    --bg-color: #f0f2f5;
    --canvas-bg-color: #ffffff;
    --node-bg-color: #e9ecef;
    --node-border-color: #ced4da;
    --text-color: #343a40;
    --connection-color: #adb5bd;
    --grid-color: rgba(0,0,0,0); /* 彻底隐藏网格 */
}

body, html {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
}

#app-container {
    width: 100%;
    height: 100%;
}

#canvas-container {
    width: 100%;
    height: 100%;
}

#main-svg {
    width: 100%;
    height: 100%;
    background-color: var(--canvas-bg-color);
    display: block;
}

#ui-container {
    position: absolute;
    top: 10px;
    right: 10px;
    z-index: 100;
    display: flex;
    gap: 10px;
    background-color: rgba(42, 42, 46, 0.8);
    padding: 8px;
    border-radius: 8px;
    backdrop-filter: blur(5px);
    flex-wrap: wrap; /* Allow wrapping on smaller screens */
}

.light-theme #ui-container {
    background-color: rgba(255, 255, 255, 0.8);
}

.control-group {
    display: flex;
    align-items: center;
    gap: 8px;
    border-left: 1px solid var(--node-border-color);
    padding-left: 10px;
}

.control-group:first-child {
    border-left: none;
    padding-left: 0;
}

button {
    background-color: var(--node-bg-color);
    color: var(--text-color);
    border: 1px solid var(--node-border-color);
    padding: 8px 12px;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s, border-color 0.2s;
}

button:hover {
    background-color: #5a5a62;
    border-color: var(--accent-color);
}

/* --- Enhanced Anchor Point Styles --- */
.node-group .anchor-point {
    opacity: 0;
    transform: scale(0.5);
    transition: opacity 0.2s ease-in-out, transform 0.2s ease-in-out;
    fill: var(--accent-color);
    stroke: white;
    stroke-width: 2px;
    cursor: crosshair;
    pointer-events: none; /* Block interaction when invisible */
}

.node-group.show-anchors .anchor-point,
.node-group:hover .anchor-point {
    opacity: 1;
    transform: scale(1);
    pointer-events: all; /* Allow interaction when visible */
    filter: drop-shadow(0 0 3px var(--accent-color));
}

.anchor-point:hover {
    transform: scale(1.3);
    filter: drop-shadow(0 0 6px white);
}

/* --- Enhanced Node Selection Styles --- */
.node-group.selected > rect {
    stroke: var(--accent-color);
    stroke-width: 3;
    filter: drop-shadow(0 0 8px var(--accent-color));
}

.node-group.multi-selected > rect {
    stroke: #ffc107;
    stroke-width: 2;
    filter: drop-shadow(0 0 6px #ffc107);
}

.node-group.selected.multi-selected > rect {
    stroke: var(--accent-color);
    stroke-width: 3;
    filter: drop-shadow(0 0 8px var(--accent-color));
}

/* --- UI Controls --- */
#animation-controls button {
    background-color: var(--node-bg-color);
    color: var(--text-color);
    border: 1px solid var(--node-border-color);
    padding: 8px 12px;
    margin-left: 5px;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s, border-color 0.2s;
}

#animation-controls button:hover {
    background-color: var(--node-border-color);
    border-color: var(--accent-color);
}

/* Ensure consistent spacing for all buttons in animation-controls */
#animation-controls button:not(:first-child) {
    margin-left: 10px;
}

/* --- Touch-friendly styles --- */
@media (max-width: 768px) {
    .anchor-point {
        r: 8 !important; /* Larger touch targets on mobile */
    }
    
    button {
        padding: 12px 16px; /* Larger buttons for touch */
        font-size: 16px; /* Prevent zoom on iOS */
    }
}

/* --- Selection box styles --- */
#selection-box {
    pointer-events: none;
}

/* --- Enhanced connection preview styles --- */
.connection-preview {
    pointer-events: none;
}

/* --- Grid background --- */
#background-grid {
    opacity: 0.1;
}

/* --- Performance optimizations --- */
.node-group {
    will-change: transform;
}

.anchor-point {
    will-change: opacity, transform;
}

.slider-container {
    display: flex;
    align-items: center;
    gap: 5px;
}

input[type="range"] {
    cursor: pointer;
}

.grid-line {
    stroke: var(--grid-color);
    transition: stroke 0.3s ease; /* Smooth transition for grid color */
    stroke-width: 3.5px;
}

/* --- Enhanced Anchor Point Styles --- */
.node-group .anchor-point {
    opacity: 0;
    transform: scale(0.5);
    transition: opacity 0.2s ease-in-out, transform 0.2s ease-in-out;
    fill: var(--accent-color);
    stroke: white;
    stroke-width: 2px;
    cursor: crosshair;
    pointer-events: none; /* Block interaction when invisible */
}

.node-group.show-anchors .anchor-point,
.node-group:hover .anchor-point {
    opacity: 1;
    transform: scale(1);
    pointer-events: all; /* Allow interaction when visible */
    filter: drop-shadow(0 0 3px var(--accent-color));
}

.anchor-point:hover {
    transform: scale(1.3);
    filter: drop-shadow(0 0 6px white);
}

/* --- Connection Creation Animation --- */
/* 关键备注：这个动画让新创建的连接以"描边绘制"的效果出现 */
/* 原理：使用 stroke-dasharray 和 stroke-dashoffset 创建绘制效果 */
.connection {
    fill: none;
    stroke: var(--connection-color);
    stroke-width: 2;
    transition: stroke 0.3s ease;
}

/* 新连接的特殊样式类 */
.connection-new {
    /* 关键备注：这些值会被JavaScript动态替换为实际的路径长度 */
    stroke-dasharray: 1000; /* 临时值，会被JS替换 */
    stroke-dashoffset: 1000; /* 临时值，会被JS替换 */
    animation: stroke-draw 0.8s ease-out forwards;
}

/* 关键备注：这是核心动画，stroke-dashoffset从路径长度变为0，创造绘制效果 */
@keyframes stroke-draw {
    to {
        stroke-dashoffset: 0;
    }
}