itch.io

I did all 50 levels with all tower and magic levels maxed and got a "skeleton levels complete" message.
Even with all upgrades its not 100% that you make it, depends on how many mobs come from the sides, and you can get killed in 3-4 hits. 
Needs less grind, more balancing and a better reward from winning than a 1 second message, but hey it was fun!

I have done up to 44 level with max: atk speed, range, armor, health, lifesteal, regen.
I think attack speed and armor are the two most important upgrades.
Going to 50 might be impossible, but i will try to max everything and test it!

I have gone up to level 33 now. My armor is maxed and no matter my attack speed 9 out of 10 enemies run to base before i hit them and some reach the base from the sides before my arrow goes out of the base... I agree with the incremental idea, but the balance is way off at later levels, you can't tank them and you can't hit them for lifesteal!

A few suggestions:
1) Some enemies have to walk less than half of the others before they hit you because they hit the castle at the sides. You should probably have a round hitbox.
2) Enemies move speed is scaling to fast, by level 20 almost every enemy just hits the castle before you get to attack.
3) There should probably be more upgrades, like arrow speed, aoe attacks and enemy debuffs.
4) Skills needs a spell check(attack, not atack) and a description.