Fix incorrect count of active mushrooms when Spider moves.
Fix incorrect calculation to decide if the flea should appear.
Increase score for flea and snail.
Fix spider not destroying entire mushroom.
Fix centipede when falling straight down could stop falling when split into two.
Handle player regeneration after losing a life.
Fix player walking through spider/flea without dieing if moving in opposite direction.
Handle 'GameOver' sequence.
Add level transition.
Increase length of centipede with each level.