Changelog

Changelog v1.4
- added more levels
- fixed wall collisions
- refined sfx

Changelog v1.3
- added hurt state to alien2
- added 1 bullet knockback to alien2

Changelog v1.2
- removed meteors
- added shield feature
- added line as a visual cue
- increased vertical space from 11 to 13

Changelog v1.1
- increased vertical space from 9 to 11
- added a tutorial level and edited dialogue to ease players in
- added white arrows to guide player
- added more messages
- made earlier levels easier with more buffer time
- added meteors