Thank you everybody for the feedback so far. Let me know in the comments if there is anything else you want me to add or fix.
I have added one new enemy to level 6 to make the level more fun please let me know what you think. See below for patch notes.
On the next patch I will focus to implement the Horde Mode. After that I will create Hard mode.
Patch Notes:
1. New enemy on level 6
2. Improvements to framerate