#t21-game-container {
    background: #ffffff;
    border: 4px solid #f0f0f0;
    border-radius: 20px;
    padding: 30px;
    text-align: center;
    max-width: 600px;
    margin: 20px auto;
    font-family: sans-serif;
}

#t21-instruction { color: #333; margin-bottom: 40px; }

.t21-canvas {
    display: flex;
    flex-direction: column;
    gap: 50px;
    align-items: center;
}

.t21-source-area, .t21-target-area {
    display: flex;
    gap: 40px;
    justify-content: center;
}

.t21-box {
    width: 90px;
    height: 90px;
    border-radius: 15px;
    cursor: grab;
    box-shadow: 0 6px 0 #bbb;
}

.t21-dropzone {
    width: 100px;
    height: 100px;
    border: 5px dashed #ddd;
    border-radius: 50%;
    transition: all 0.3s;
}

#t21-message {
    height: 40px;
    margin: 20px 0;
    font-size: 24px;
    font-weight: bold;
    color: #27ae60;
}

#t21-reset {
    padding: 15px 30px;
    font-size: 18px;
    background: #3498db;
    color: white;
    border: none;
    border-radius: 10px;
    cursor: pointer;
}