Bug for faster leveling, when you die you keep any upgrades but your soul count goes back to what it was at the start of the level. So, get a lot of souls and then finish a level without spending them, then during the next level buy something, die, restart and you have the upgrade and enough souls to buy another. Repeat to liking.
@Fabiomeister, more powerful enimies are harder to hit so you have a lower%, but when your weapon ATK or tactic skills level up you get better at hitting.
@chinor, at first you can only play the yellow mission in the top left.
@UnleasherOfDoom, click the yellow money symbol in the bottom right of your money indicator.
If you go too long in the survival mode the combat stops animating properly, units will stop moving, hp meters appear where there aren't any units, and things not dying when they are supposed to.