Enemy Variance, Difficulty Scaling, Enemy Variation, Pause, Death, Score

Added pause (Press escape or backspace or p)

Added temporary death page. Press pause to return to main menu

Added Score

Added enemy variants!

1. Pink frog - Faster and even more uncontrollable
2. Big Frog - Slow but tanky

Added temporary difficulty scaling, enemies will spawn in bigger bunches and harder variants as time goes on.