Glad to know your thoughts regarding the given instructions, mechanics, and art!
As for the waves, I haven't thought about that, but I had the idea that such numbers would increase after a certain amount of time has passed in means of changing the spawn rate, i.e., via the spawner's timer. I'll take your suggestion in consideration!
Also regarding the time for resting, certainly it would be a good factor in the gameplay as aside for taking a break, it could be also applied for getting upgrades from a shop, etc. I'll add this one to the To-do list too.