Interesting concept. I think i found a bug where if you just keep building a tower of pebbles by dropping them on each other. Each pebble will have more and more gap between them. Also this is the easiest way to climb. You basically create your own stairs and don't care about anything else. You even can place a block on the same block you standing but little bit to the side. I don't think this is intended.
Viewing post in Ink Tower jam comments
The pebble placing was pretty buggy in the last build I could upload before the deadline, but I think I ended up fixing that gap bug and some other pebble placing bugs afterwards. I'll probably upload the fixed version sometime after the end of the jam. Being able to lock pebbles next to each other is intended, though. I do think I need to figure out a way to better incentivize not just stacking straight up though. Thanks for the feedback!