:root {
            --paper-color: #fcfcfc;
            --ink-color: #2d3748;
            --highlight-color: #f6ad55; /* 荧光笔黄 */
            --accent-blue: #4299e1;     /* 圆珠笔蓝 */
        }

        body {
            background-color: var(--paper-color);
            background-image: radial-gradient(#cbd5e0 1px, transparent 1px);
            background-size: 20px 20px;
            color: var(--ink-color);
            font-family: 'ZCOOL KuaiLe', cursive, sans-serif; /* 使用手写字体 */
            overflow-x: hidden;
        }

        /* 手绘边框效果 CSS Generator */
        .sketch-box {
            border: 2px solid var(--ink-color);
            border-radius: 255px 15px 225px 15px / 15px 225px 15px 255px;
            background: white;
            box-shadow: 2px 3px 0px rgba(0,0,0,0.1);
            transition: all 0.2s ease-in-out;
        }

        .sketch-box:hover {
            border-radius: 15px 225px 15px 255px / 255px 15px 225px 15px;
            box-shadow: 4px 5px 0px rgba(0,0,0,0.2);
            transform: translateY(-2px) rotate(-1deg);
        }

        /* 按钮风格 */
        .sketch-btn {
            background: var(--ink-color);
            color: white;
            border-radius: 255px 15px 225px 15px / 15px 225px 15px 255px;
            padding: 0.75rem 2rem;
            font-size: 1.25rem;
            cursor: pointer;
            transition: transform 0.1s;
            display: inline-block;
        }
        
        .sketch-btn:hover {
            transform: scale(1.05) rotate(2deg);
            background: #1a202c;
        }

        .sketch-btn:active {
            transform: scale(0.95);
        }

        /* 荧光笔高亮效果 */
        .highlight {
            background: linear-gradient(120deg, rgba(246, 173, 85, 0) 0%, rgba(246, 173, 85, 0.4) 100%);
            background-repeat: no-repeat;
            background-size: 100% 40%;
            background-position: 0 88%;
        }

        /* 涂鸦动画 */
        @keyframes draw {
            from { stroke-dashoffset: 1000; }
            to { stroke-dashoffset: 0; }
        }

        .doodle-svg path {
            stroke-dasharray: 1000;
            stroke-dashoffset: 1000;
            animation: draw 2s ease-in-out forwards;
        }
        
        /* 3D 书籍效果 */
        .book-container {
            perspective: 1000px;
        }
        
        .book {
            width: 260px;
            height: 360px;
            position: relative;
            transform-style: preserve-3d;
            transform: rotateY(-25deg) rotateX(5deg);
            box-shadow: 15px 15px 20px rgba(0,0,0,0.2);
            transition: transform 0.5s;
        }
        
        .book:hover {
            transform: rotateY(-15deg) rotateX(0deg) scale(1.02);
        }

        .book-spine {
            position: absolute;
            top: 0;
            left: 0;
            width: 40px;
            height: 100%;
            background: #000;
            transform: rotateY(90deg) translateZ(-20px);
            border-left: 2px solid white;
        }

        /* 导航栏手绘下划线 */
        .nav-link {
            position: relative;
        }
        .nav-link::after {
            content: '';
            position: absolute;
            width: 100%;
            height: 2px;
            bottom: -5px;
            left: 0;
            background-color: var(--accent-blue);
            visibility: hidden;
            transform: scaleX(0);
            transition: all 0.3s ease-in-out;
            border-radius: 50% 20% / 10% 40%;
        }
        .nav-link:hover::after {
            visibility: visible;
            transform: scaleX(1);
        }

        .hand-drawn-arrow {
            transform: rotate(10deg);
        }