:root {
    --background-color: #121212;
    --text-color: #ffffff;
    --text-shadow-color: #000000;
    --link-color: #cccccc;
    --link-hover-color: #2a2a2a;
    --menu-background-color: #1a1a1a;
    --input-background-color: #333;
    --input-border-color: #888;
    --input-focus-background-color: #444;
    --keyboard-key-expended-color: gray;
    --keyboard-key-expended-background-color: #1a1a1a;
    --button-background-color: #333;
    --button-hover-background-color: #2a2a2a;
    --correct-color: #4caf50;
    --present-color: #b59f3b;
    --absent-color: #333;
    --notification-background-color: #333;
    --popup-background-color: #1a1a1a;
    --popup-text-shadow: 2px 2px 4px #000000;
    --close-popup-hover-color: #ff0000;
    --calendar-hover-background-color: #555;
}