body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    background-color: #e6ffe6; /* Light green background */
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: #333;
}

.container {
    background-color: #ffffff;
    padding: 40px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 100, 0, 0.1); /* Greenish shadow */
    text-align: center;
    width: 90%;
    max-width: 500px;
}

h1 {
    color: #28a745; /* Medium green heading */
    margin-bottom: 30px;
    font-size: 2.5em;
}

.input-section {
    margin-bottom: 40px;
}

label {
    display: block;
    font-size: 1.2em;
    margin-bottom: 15px;
    color: #4CAF50; /* Slightly darker green for label */
}

input[type="date"] {
    padding: 12px 15px;
    font-size: 1.1em;
    border: 2px solid #4CAF50; /* Green border */
    border-radius: 8px;
    outline: none;
    cursor: pointer;
    background-color: #f0fff0; /* Very light green input background */
    color: #333;
    width: calc(100% - 34px); /* Adjust for padding and border */
    max-width: 250px;
    transition: border-color 0.3s ease;
}

input[type="date"]:focus {
    border-color: #28a745; /* Darker green on focus */
}

.dday-result {
    margin-top: 30px;
}

#dday-display {
    font-size: 4.5em; /* Large number */
    font-weight: bold;
    color: #008000; /* Dark green for the D-Day number */
    display: block; /* Ensures it takes full width */
    min-height: 1.5em; /* Prevent layout shift before number appears */
}