this is awesome! I did not expect putting so mutch time in a jam game, I max out every update and played till my browser crashed because there where to many units on the screen :D
The Idea is really simple and with the active part (aiming) it is really engaging. I also like that in the beginning it is way to hard so you die after few seconds, but get enouth money to buy updates and try again. I think that whats keept me hooked.
Few things I would suggest:
- make the icons in the upgrade window bigger, they feel a little bit los
- use the same pixel per unit in all your assets, some pixels are smaller some bigger.
- better UI for timer and the quest text ("survive X"), they where not notable for me while playing
- The UI font is fine but not suited for smaller text, maby use a alternative one for smaller text to make it more readable
Otherwise if you add new content will definitly play it again! amazing work! :)