:root {
    --bg-color: #f4f4f4;
    --text-color: #333;
    --card-bg-color: #fff;
    --header-bg: #333;
    --header-text: #fff;
    --accent-color: #007bff;
    --input-border: #ccc;
}

[data-theme='dark'] {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --card-bg-color: #2d2d2d;
    --header-bg: #111;
    --header-text: #fff;
    --accent-color: #4da3ff;
    --input-border: #444;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

header {
    background: var(--header-bg);
    color: var(--header-text);
    padding: 1rem 2rem;
    text-align: center;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

header h1 {
    margin: 0;
    font-size: 1.5rem;
}

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

#diet-plan {
    background: var(--card-bg-color);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    margin-top: 1.5rem;
    transition: background-color 0.3s;
}

user-input-form {
    display: block;
    background: var(--card-bg-color);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    transition: background-color 0.3s;
}

#theme-toggle {
    background: transparent;
    border: 1px solid var(--header-text);
    color: var(--header-text);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s;
}

#theme-toggle:hover {
    background: var(--header-text);
    color: var(--header-bg);
}