body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #fafafa;
    color: #333;
}
header {
    background-color: #3f51b5;
    color: #fff;
    padding: 1rem;
    text-align: center;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}
main {
    padding: 1rem;
}
input[type="text"], input[type="number"] {
    padding: 0.5rem;
    margin-right: 0.5rem;
}
button {
    padding: 0.5rem 1rem;
    margin: 0.5rem 0.25rem;
    border: none;
    background-color: #3f51b5;
    color: #fff;
    box-shadow: 0 2px 2px rgba(0,0,0,0.2);
    cursor: pointer;
}
button:hover {
    background-color: #303f9f;
}
.hidden {
    display: none;
}
#task-display {
    font-size: 1.5rem;
    margin: 1rem 0;
}
#countdown {
    font-size: 1.2rem;
    color: #d32f2f;
}
.notification {
    animation: blink 1s step-end infinite alternate;
}
@keyframes blink {
    from { background-color: inherit; }
    to { background-color: #ffeb3b; }
}