Elemental bolt tower upgrades

[MAKAIROSI]

So i'm at the point that i need to upgrade it to a specific element. Here's my question: does its damage completely change to that element, or do they keep some of their previous "global" damage?

Also, is there a "safe" element? I mean, i've seen fire elementals, so fire will probably do 0 damage to them. What element would you suggest that will work with most enemies? I'm a returning player, though the game feels almost new to me.

[Midori Mayu]

from the in-game tower tooltip, I'm guessing the elemental damage is added on top of it's previous damage type? like 20 crushing + 30 Ice damage per shot.

also from in-game mob details, it seems Ice is the best upgrade at the moment (against ice weak Fire elementals/Specters/ Slime(partially). Lightning is best for Slimes/Blood Slimes. and Fire is best for the other regular mobs.

[MAKAIROSI]

Thanks, this was quite helpful. I'll go for ice asap :)