You can interact with special blocks like the enhancer with [E] and put dirt or other blocks in them to change them into others (not all blocks can be combined or enhanced, they will just stay in the intractable block without turning into anything (you can remove them again with [E])). Dead jombies can also be picked up that way (with [E]). I should've added a hint in the UI indicating that, pretty easy to miss. After you have tried a few recipes you might be able to create steel, which is the base for most "special" blocks (blocks that do something, like towers (idk why i named them tower and not turret) ) hint: steel+flesh is a good combination. Depending on what blocks you have acquired you can build a little base with defense against the jombies. why not just build up or build a closed bunker? well because the jombies can destroy blocks and will dig staircases or just break your block-tower from the base, which will fully destroy it (this isnt minecraft 😜, there are no floating blocks). the longer you stay alive the harder the waves will get (bottom left number), meaning more jombies and harder jombies (3 versions rn).
if you want jombies to not constantly break your walls , use a harder block (stone instead of dirt for example), as the jombies pathfinding always go for the easiest path (which can even be through a wall instead of a open way), so enforce where you don't want jombies to go through.
so tl;dr: create useful blocks through interaction [E] with the enhancer,combiner (and splitter (has less uses)) to build up a defense against the jombies.
let me know, if you play the game again, but thx for trying it in this state regardless :D.