Thanks for the feedback! Glad you enjoyed the concept :D
Yes objects and enemies are "randomly" placed at the start of the game, think of it like a scratchcard as you place pipes (or dig tunnels).
You're right that there's a lot of UI missing - and most of the things you touched on are in the plan. I like the idea of animating the upcoming pipes, that will definitely make it clearer which direction they're arriving from.
In terms of introducing the mechanics etc. the current plan is that there will be a series of levels where tiles are introduced one at a time. E.g. the first level will be only coins. On every level, the number of coins you exit with will be your score, which will then give a 1-3 star rating, then stars are spent on unlocking new heroes (with different starting gear or abilities). So each level will be standalone with the objective of getting the most coins.
What I'm still figuring out is how I could also make a "true" dungeon crawling mode, where the hero and any gear they have carry over to the next level (sort of like the game Hoplite).
Recently I've been updating the art - moving to a 16x16 tileset. Not all tiles are finished but here's a recent mockup:
