:root {
    --primary-color: #0070ba;
    --secondary-color: #009cde;
    --background-color: #f7f9fa;
    --card-background: #ffffff;
    --text-color: #333;
    --light-text-color: #666;
    --border-color: #e1e4e8;
    --box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    --border-radius: 8px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    margin: 0;
    padding: 20px;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 100vh;
}

.container {
    width: 100%;
    max-width: 600px;
    background-color: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    overflow: hidden;
}

header {
    background-color: var(--primary-color);
    color: white;
    padding: 20px;
    text-align: center;
}

header h1 {
    margin: 0 0 5px 0;
    font-size: 24px;
}

header p {
    margin: 0;
    opacity: 0.9;
}

.language-selector {
    margin-top: 15px;
}

.language-selector button {
    background: none;
    border: 1px solid white;
    color: white;
    padding: 5px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 14px;
    opacity: 0.7;
    transition: opacity 0.2s, background-color 0.2s;
}

.language-selector button:hover {
    opacity: 1;
}

.language-selector button.active {
    background-color: white;
    color: var(--primary-color);
    opacity: 1;
}

main {
    padding: 30px;
}

.calculator {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.input-group {
    display: flex;
    flex-direction: column;
}

.input-group label {
    margin-bottom: 8px;
    font-weight: 600;
    font-size: 14px;
    color: var(--light-text-color);
}

input[type="number"], select {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-size: 16px;
    box-sizing: border-box; /* Important for consistent sizing */
    background-color: #fff;
}

input[type="number"]:focus, select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 2px rgba(0, 112, 186, 0.2);
}

#calculate-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 15px;
    border-radius: 6px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    transition: background-color 0.2s;
}

#calculate-btn:hover {
    background-color: #005ea6;
}

.result-container {
    margin-top: 30px;
    padding: 20px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background-color: var(--background-color);
}

.result-container.hidden {
    display: none;
}

.result-container h2 {
    margin-top: 0;
    font-size: 20px;
    text-align: center;
    color: var(--primary-color);
}

.result-item {
    display: flex;
    justify-content: space-between;
    font-size: 18px;
    padding: 15px 0;
    border-bottom: 1px solid var(--border-color);
}

.result-item:last-of-type {
    border-bottom: none;
}

.result-item span {
    color: var(--light-text-color);
}

.result-item strong {
    font-weight: 600;
}

.note {
    font-size: 12px;
    color: var(--light-text-color);
    text-align: center;
    margin-top: 20px;
}

footer {
    background-color: var(--background-color);
    text-align: center;
    padding: 15px;
    font-size: 12px;
    color: var(--light-text-color);
}