body {
    font-family: system-ui, sans-serif;
    max-width: 480px;
    margin: 2rem auto;
    padding: 0 1rem;
}
canvas {
    border: 1px solid #333;
    background: #fff;
    touch-action: none;
    display: block;
}
.controls { margin: 0.5rem 0 1rem 0; }
button {
    padding: 0.5rem 1rem;
    margin-right: 0.5rem;
    font-size: 1rem;
}
#result {
    font-size: 1.25rem;
    min-height: 1.5rem;
    margin-bottom: 1rem;
}
#history li { font-family: monospace; }