body {
    font-family: Arial;
    padding: 20px;
    background: #f0f0f0;
}
h1 { margin-bottom: 20px; }
#canvas {
    width: 100%;
    height: 500px;
    border: 2px solid #333;
    background: #fff;
    position: relative;
    margin-top: 20px;
}
.node {
    width: 100px;
    height: 50px;
    background: #4a90e2;
    color: white;
    text-align: center;
    line-height: 50px;
    border-radius: 6px;
    position: absolute;
    cursor: grab;
}