:root {
    --background-color: #f0f2f5;
    --text-color: #333;
    --card-background: #ffffff;
    --button-background: #4a90e2;
    --button-text-color: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
    --background-color: #2c3e50;
    --text-color: #ecf0f1;
    --card-background: #34495e;
    --button-background: #5dade2;
    --button-text-color: #ffffff;
    --shadow-color: rgba(0, 0, 0, 0.4);
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: var(--background-color);
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

.theme-switcher {
    position: absolute;
    top: 20px;
    right: 20px;
}

#theme-toggle {
    display: none;
}

#theme-toggle + label {
    display: inline-block;
    width: 50px;
    height: 26px;
    background-color: #ccc;
    border-radius: 13px;
    position: relative;
    cursor: pointer;
    transition: background-color 0.3s;
}

#theme-toggle + label::after {
    content: '';
    position: absolute;
    width: 22px;
    height: 22px;
    background-color: white;
    border-radius: 50%;
    top: 2px;
    left: 2px;
    transition: transform 0.3s;
}

#theme-toggle:checked + label {
    background-color: #4a90e2;
}

#theme-toggle:checked + label::after {
    transform: translateX(24px);
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    margin: -1px;
    padding: 0;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}