What I've found so far:
- Ladder-blocks let you move up and down
- Clouds let you build sideways
- Hitting the bell reveals hidden parts of the map, which the eagle does as well when it shows up
- Placing any block in the top row creates fire, which burns any block you place on it except ladders, which it climbs
- Fire transfers from map to map, and destroys blocks when you move up and down between maps
- Whatever block you reach at the top/bottom of a map will have a ladder above/below it. Until you go to the next screen, it isn't generated. That means you can dig unlimited ladders out of the bottom of the screen.
Not figured out yet:
- You can collect black dots, not clear what they do or if the game keeps track of how many
- A worm sometimes appears from the side of a block. Unclear what it does
- A line circles around the screen cyclically. There is a rumor that it reveals some information
- Going in different directions doesn't seem to reveal anything new, other than more underground/sky