/* Basic Reset */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --background-color: #f3f4f6;
    --card-background: #ffffff;
    --text-color: #1f2937;
    --text-muted: #4b5563;
    --border-radius: 8px;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

[data-theme="dark"] {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --background-color: #0f172a;
    --card-background: #1e293b;
    --text-color: #f8fafc;
    --text-muted: #94a3b8;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.24);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.5;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.theme-toggle-container {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
}

#theme-toggle-btn {
    background-color: var(--card-background);
    color: var(--text-color);
    border: 1px solid var(--text-muted);
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    box-shadow: var(--shadow);
    transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, transform 0.2s ease;
}

#theme-toggle-btn:hover {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
    transform: scale(1.05);
}

#theme-toggle-btn:active {
    transform: scale(0.95);
}

.card {
    background-color: var(--card-background);
    padding: 30px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    margin-bottom: 30px;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

.card h2, .card p, header h1, header p, footer p, button {
    transition: color 0.3s ease, background-color 0.3s ease;
}

.card h2 {
    font-size: 1.5rem;
    margin-bottom: 15px;
}

.card p {
    color: var(--text-muted);
    margin-bottom: 20px;
}

button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

button:hover {
    background-color: var(--primary-hover);
}

#result-message {
    margin-top: 20px;
    font-weight: bold;
    color: var(--primary-color);
    transition: opacity 0.3s ease;
}

.hidden {
    display: none;
    opacity: 0;
}

footer {
    font-size: 0.875rem;
    color: var(--text-muted);
}