* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Arial', sans-serif;
}

body {
    background-color: #f4f7fa;
    padding: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

.container {
    max-width: 600px;
    width: 100%;
    background-color: white;
    padding: 30px;
    border-radius: 15px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

header {
    text-align: center;
    margin-bottom: 30px;
}

h1 {
    color: #2c3e50;
    font-size: 28px;
    margin-bottom: 10px;
}

header p {
    color: #7f8c8d;
    font-size: 16px;
}

.calculator-form {
    background-color: #f9f9f9;
    padding: 20px;
    border-radius: 10px;
    margin-bottom: 20px;
}

.form-group {
    margin-bottom: 15px;
}

label {
    display: block;
    margin-bottom: 5px;
    color: #34495e;
    font-weight: bold;
}

input[type="date"] {
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
    width: 100%;
    font-size: 16px;
    background-color: #fff;
    transition: border-color 0.3s;
}

input[type="date"]:focus {
    border-color: #3498db;
    outline: none;
}

button {
    padding: 12px;
    background-color: #3498db;
    color: white;
    border: none;
    border-radius: 5px;
    width: 100%;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: #2980b9;
}

.result-section {
    background-color: white;
    padding: 20px;
    border-radius: 10px;
    border: 1px solid #ddd;
    margin-top: 20px;
    display: none;
}

.green-header {
    background-color: #4CAF50;
    color: white;
    padding: 10px;
    border-radius: 5px 5px 0 0;
    font-size: 20px;
    margin: -20px -20px 20px -20px;
    text-align: center;
}

.result-section p {
    color: black;
    font-size: 16px;
    line-height: 1.6;
}

.collapsible {
    background-color: #f9f9f9;
    margin: 10px 0;
    padding: 15px;
    border-radius: 5px;
    cursor: pointer;
    font-weight: bold;
    color: #2c3e50;
    transition: background-color 0.3s;
}

.collapsible:hover {
    background-color: #e0e0e0;
}

.content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease-out;
    padding: 0 15px;
}

.content.show {
    max-height: 1000px;
    padding: 15px;
}

ul, ol {
    padding-left: 20px;
}

ul li::before {
    content: "✔️";
    color: #27ae60;
    margin-right: 5px;
}

footer {
    text-align: center;
    margin-top: 30px;
    color: #7f8c8d;
    font-size: 14px;
}

@media (max-width: 600px) {
    .container {
        padding: 15px;
    }

    h1 {
        font-size: 24px;
    }

    button, input[type="date"] {
        font-size: 14px;
    }
}