:root {
    --bg-color: #111;
    --text-color: #fff;
    --card-bg: #222;
    --circle-bg: #333;
    --primary-color: #4CAF50;
    --primary-hover: #45a049;
    --shadow-color: rgba(0, 0, 0, 0.5);
    --transition-speed: 0.3s;
}

.light-mode {
    --bg-color: #f4f4f9;
    --text-color: #333;
    --card-bg: #fff;
    --circle-bg: #e0e0e0;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

main {
    text-align: center;
    padding: 2rem;
    max-width: 600px;
    width: 100%;
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

p {
    margin-bottom: 2rem;
    opacity: 0.8;
}

#theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    background: var(--card-bg);
    border: 1px solid var(--circle-bg);
    color: var(--text-color);
    padding: 10px;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.2rem;
    box-shadow: 0 2px 10px var(--shadow-color);
    transition: transform 0.2s ease, background-color var(--transition-speed);
    display: flex;
    align-items: center;
    justify-content: center;
    width: 45px;
    height: 45px;
}

#theme-toggle:hover {
    transform: scale(1.1);
}