How to play Maggotmania on Mac

Maggotmania is a single screen shooter inspired by the arcade game Centipede where you control a blue creature at the bottom of the screen trying to destroy a large maggot that appears at the top of the screen over various levels. You can move left or right, and forwards a short distance as well as move backwards and you keep firing upwards when you fire your weapon. The maggot moves across the screen and when it hits a flower or the edge of the screen then it moves down one place and moves the opposite way. When you hit the maggot, it splits into two parts and keeps moving downwards towards you leaving behind a flower. Flowers stop your bullets but after a few shots it disappears and if you hit a flower then you lose one of three lives. Other creatures make an appearance like a spider and snail and these can be shot for bonus points. If the maggot reaches the bottom of the screen then it starts to move upwards and when destroyed you move on to the next level.