body {
    font-family: 'Segoe UI', sans-serif;
    background: #f1f5f9;
    margin: 0;
}

.app {
    max-width: 420px;
    margin: auto;
    background: #fff;
    min-height: 100vh;
}

.header {
    background: #1e293b;
    color: white;
    padding: 15px;
    text-align: center;
    font-weight: bold;
}

.card {
    padding: 15px;
    border-bottom: 1px solid #eee;
}

button {
    width: 100%;
    padding: 12px;
    border: none;
    background: #2563eb;
    color: white;
    border-radius: 6px;
    margin-top: 10px;
}

.timer {
    text-align: center;
    font-size: 18px;
    color: red;
}