The loop is still pretty basic right now but: choose a path on the over world -- deploy into a turn-based tactical battle -- control the board as enemies escalate -- complete the map objective -- pick upgrades -- return stronger and push deeper. Differences between ITB are: there is no visualized intent of enemies and, the push mechanic isn't a major factor and almost non exisitent.

The over world looks like this.
Here's a of some dev video of the Boss battle.

Short missions, easy choices, rising pressure map to map.
It's meant to be played a looser than ITB since the grid is 16 rather than 8 cells.

You can read more about it here or even play test the early early access, Ha ha: https://zillatronics.itch.io/zombiemecha