The idea just struck me-- what sould Minecraft look like on the 2600?
I've been working on that concept on & off for several months but its been hard to find a balance of the gameplay features (sprites) and the rendering limits on the 2600. I'd agree with Rex Dart that it would look something like Dig Dug in that the player carves paths through a Playfield graphic so the same basic engine concept as DD. I've mostly used Terraria as reference for what I'd like it to look like but its not as easy as it seems.
I guess you could use mid-line color changes coupled with color changes per scanline within a Playfield graphic to create regions of different block material colors (Stone/Water/Gold) and use both Missiles set to Playfield bit width to make organic outer edges to those Playfield regions. The alternative to that would be a flicker based Interlaced Multicolored Playfield system like SeaGTGruff is working on which frees the Missiles up but has specific color restrictions to compensate for its visible flicker byproducts.
I thought it might possible to do a lighting system based on clipping the Playfield using blocks of dither pattern but I don't have the know how to even try such an undertaking. I think it would be one of those situations where it would work but nothing else could be going on at the same time lol.
The other major challenge is getting items, monsters, and the player rendering on the same scan lines on account of the customizing nature of the games environment. There is basic sprite work division as in Player0 is the Miner, Player1 is the monster, and the Missiles and or Ball are the items. With bit constructed sprites you can put some on odd scan lines and the other on even scan lines if you skip scan lines or use an alternating scan line renderer with some flicker to extend things a bit.
For items I used a banded separation setup where tables, wall hangings, and lighting fixtures could only exist in there respective vertical positions within the "wall' height which is an example of a logical restriction. You can also use monster fiction to keep monsters at there respective vertical positions like vampires die in sunlight, slimes prefer dark caves, woodland creatues flee dark caverns, etc.
If you ever take a go at it don't do what I did and try to make it pretty since Minecraft is more about function than beauty so stay true to that original spirit.