A very cute, fun little game! I agree that it's a little confusing what all the tower types do. I also died in one shot to a mortar enemy, which I wasn't sure was fair?
You must have been hurt, probably by having a few soldiers slip through you! They actually do 4 ticks of damage, of 10 maximum. They need 3 shots to kill you! I should probably lower that, though i have some things planned for artillery to nerf them a bit.