body {
    background-color: #222;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    font-family: sans-serif;
    color: white;
}

.container { text-align: center; }

#start-btn {
    padding: 10px 20px;
    margin-bottom: 20px;
    cursor: pointer;
    background: #444;
    color: white;
    border: 1px solid #666;
    border-radius: 5px;
}

#piano {
    display: flex;
    position: relative;
    padding: 20px;
    background: #111;
    border-radius: 10px;
}

.key {
    position: relative;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: flex-end;
    padding-bottom: 10px;
    user-select: none;
}

.white {
    width: 60px;
    height: 200px;
    background: white;
    border: 1px solid #ccc;
    color: #999;
    z-index: 1;
}

.black {
    width: 40px;
    height: 120px;
    background: #000;
    color: white;
    margin-left: -20px;
    margin-right: -20px;
    z-index: 2;
    border-radius: 0 0 3px 3px;
}

.key.active {
    background: #ffcc00;
}

.key span { font-size: 12px; pointer-events: none; }