:root {
    --bg-color: #ffffff;
    --text-color: #333333;
    --h1-color: #333333;
    --text-shadow: none;
    --btn-bg: #4CAF50;
    --btn-hover: #45a049;
}

[data-theme="dark"] {
    --bg-color: #1a2a3a;
    --text-color: #ffffff;
    --h1-color: #ffffff;
    --text-shadow: 0 0 5px #fff, 0 0 10px #fff, 0 0 15px #0073e6, 0 0 20px #0073e6, 0 0 25px #0073e6, 0 0 30px #0073e6, 0 0 35px #0073e6;
    --btn-bg: #4CAF50;
    --btn-hover: #45a049;
}

body {
    font-family: sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}

h1 {
    text-align: center;
    color: var(--h1-color);
    font-size: 3em;
    margin-bottom: 40px;
    text-shadow: var(--text-shadow);
    transition: text-shadow 0.3s;
}

.theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    padding: 10px;
    cursor: pointer;
    background: var(--btn-bg);
    color: white;
    border: none;
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

.theme-toggle:hover {
    background: var(--btn-hover);
}