Interesting concept but the game stalls pretty hard in the 30s of Stage 1. Costs continue to rise exponentially but your ship upgrades stop becoming cost effective (especially frigates around level 200). I don't know exactly how many PPI you need to beat the game, but I'm well over 11M now and am tired of waiting for more.
This game is a real grind. Leveling seems very slow relative to the difficulty of the enemies, as is the supply of crystals you need to enchant your items, so you end up spending way too much time running around slaughtering weaker foes to try to gain XP and/or crystals so you can stand a chance in the next map. It stops being fun after a while and just becomes a chore.
I don't remember Crusade being this much of a grind. I can't recommend this. Progress is painfully slow and there isn't even a threadbare story to hold your interest through it.
Difficulty is *brutal* at the beginning. Headshots seem to do nothing with that puny pistol. Get a few fast zombies in the first wave and you can forget making it to day #2.
Sometimes the game just doesn't give you enough customers to reach the day's goal, meaning you can't win that day no matter what. This needs to be fixed.
There's little point to continue playing the game once you cross the "horseman starts receiving negative hit points at levelup" threshold. I understand this is a free game, but the developer should take a little pride in his work and fix such a glaring bug.
The 30,000 debt seems to be a gameplay mechanic to force you to grind it out longer. The first 20 levels get pretty easy after you pay off the debt, then Unholy Temple is insane, then after that it's downhill. There are some bugs here too with enemy spells - Soul Drain (which reads overpowered anyway) doesn't work at all and the "X Touch" spells don't seem to do as much damage as they should.
Interesting game though.