* {
    box-sizing: border-box;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

body {
    margin: 0;
    padding: 0;
    background: #f4f6f8;
    color: #1f2937;
}

.container {
    max-width: 480px;
    margin: 60px auto;
    padding: 24px;
    background: #ffffff;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.08);
}

h1 {
    margin-top: 0;
    font-size: 26px;
}

.subtitle {
    color: #6b7280;
    margin-bottom: 24px;
}

.calculator label {
    display: block;
    margin-bottom: 16px;
    font-weight: 600;
}

.calculator input[type="date"] {
    width: 100%;
    padding: 10px;
    margin-top: 6px;
    font-size: 16px;
}

.options {
    margin-bottom: 16px;
}

button {
    width: 100%;
    padding: 12px;
    background: #2563eb;
    border: none;
    color: #ffffff;
    font-size: 16px;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
}

button:hover {
    background: #1d4ed8;
}

.result {
    margin-top: 20px;
    padding: 14px;
    background: #f0f9ff;
    border: 1px solid #bae6fd;
    border-radius: 8px;
    font-weight: 600;
}

footer {
    margin-top: 30px;
    text-align: center;
    font-size: 14px;
    color: #6b7280;
}