Fun. I enjoyed discovering all the little aspects of your game and I think with a little work this would be a great coffee break type of game!
The shops are very hit or miss, went through 3 times and got pretty deep without seeing any, then on my last playthrough had one at level 2 and another at level 3.
I think a high score mechanic to try to beat your last run would make this way more interesting.
Also, with the graphical style you chose, not making the alien look like a space invader is truly a missed opportunity.