:root {
    --primary-color: #4CAF50;
    --secondary-color: #2196F3;
    --background-color: #ffffff;
    --text-color: #333333;
    --card-bg: #f5f5f5;
    --input-bg: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

.dark-mode {
    --primary-color: #66bb6a;
    --secondary-color: #42a5f5;
    --background-color: #1a1a1a;
    --text-color: #ffffff;
    --card-bg: #2d2d2d;
    --input-bg: #3d3d3d;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color 0.3s, color 0.3s;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
}

.container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 1rem;
}

h1 {
    text-align: center;
    margin-bottom: 2rem;
    color: var(--primary-color);
    font-size: 2.5rem;
    text-shadow: 2px 2px 4px var(--shadow-color);
}

.calculator {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 8px 16px var(--shadow-color);
    margin-bottom: 2rem;
}

.input-group {
    margin-bottom: 1.5rem;
}

label {
    display: block;
    margin-bottom: 0.5rem;
    color: var(--text-color);
    font-weight: 500;
}

input, select {
    width: 100%;
    padding: 0.8rem;
    border: 2px solid var(--primary-color);
    border-radius: 8px;
    background-color: var(--input-bg);
    color: var(--text-color);
    font-size: 1rem;
    transition: all 0.3s ease;
}

input:focus, select:focus {
    outline: none;
    box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.2);
}

.calculate-btn {
    width: 100%;
    padding: 1rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.calculate-btn:hover {
    background-color: #45a049;
    transform: translateY(-2px);
}

.result {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 8px 16px var(--shadow-color);
}

.result-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.result-item {
    text-align: center;
    padding: 1rem;
    background-color: var(--input-bg);
    border-radius: 8px;
    box-shadow: 0 4px 8px var(--shadow-color);
}

.result-item h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.health-advice {
    margin-top: 2rem;
    padding: 1rem;
    background-color: var(--input-bg);
    border-radius: 8px;
    box-shadow: 0 4px 8px var(--shadow-color);
}

.reset-btn {
    display: block;
    width: 100%;
    padding: 1rem;
    background-color: var(--secondary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    cursor: pointer;
    margin-top: 1rem;
    transition: all 0.3s ease;
}

.reset-btn:hover {
    background-color: #1976d2;
    transform: translateY(-2px);
}

.theme-switch {
    position: fixed;
    top: 1rem;
    right: 1rem;
}

.theme-label {
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    background-color: var(--card-bg);
    box-shadow: 0 2px 4px var(--shadow-color);
}

#theme-toggle {
    display: none;
}

.sun, .moon {
    font-size: 1.5rem;
}

.dark-mode .sun {
    display: none;
}

.light-mode .moon {
    display: none;
}

@media (max-width: 600px) {
    .container {
        margin: 1rem auto;
    }
    
    .result-grid {
        grid-template-columns: 1fr;
    }
    
    h1 {
        font-size: 2rem;
    }
}