After thinking, In TI-BASIC+xLIB/Celtic, the game design would most likely have to look like this:

That's one way to make all the blocks uniquely identifiable. The black and semi-black blocks are still a bit too ambiguous, though.

I remember Tetris Flash had a similar problem when ported to the GB. The developers decided to instead draw patterns in the blocks, as opposed to using colors. Since the blocks are 4x4, that wouldn't really be feasible.

Those could, instead, be represented as circles. It might look kind of silly, but it would definitely disambiguate them. That's just one idea off the top of my head, though.

Good idea, Zera. Thought of a half-black square. That could be triangles, also. With that we could create up to 6 types of blocks: black/white squares/circles/triangles?

EDIT: Plusses, half-squares, etc., name them. And I got ninja'd.

I didn't want to have more than three types of blocks, though. Since the game is based on trominoes, 3 is an important number: three squares per block, three types of blocks... If you add more to it, it kind of loses its theme. (that, and the difficulty would substantially increase with each new type of block that's introduced)

This is what I was thinking with DJ's idea:



Replacing the solid-black blocks with circles also disambiguates areas that would otherwise have a ton of black pixels. Since he added a white dot to the other black squares, that also helps out.

I should probably elaborate on a few more details about gameplay...

Unlike Tetris, there is no speed level. Blocks will always drop at the same speed. The only challenge against the player is the accumulation of squares in patterns that are difficult to clear. The actual "quest" mode would consist of a series of levels with predefined squares on the board. Generally, the more difficult the level, the more squares would be stacked on the board from the start. At certain heights, it would be difficult to manuever new formations as they drop.

Versus mode would allow the player to define the starting conditions, in this sense. There wouldn't be multiple levels, but a single round of play with a user-specified amount of pre-existing squares. (if any) The objective during versus mode is to survive. In this mode, scoring 5-square matches will incur a penalty against the opposing player: A solid line will appear at the bottom of their board, slightly raising their elevation.  (up to 4 lines total may be incurred per player) For every gravity-chain a player scores, the opposing player receives a solid I block. This block cannot be removed from the board under any conditions, and an infinite number of them can be incurred.

Probably something like: Lower block 4px / second

I'm only estimating this in my head. Not sure how quickly that might actually play out.

You know, if we're only going to use one gray, and it essentially can't appear in the actual playing board anyway, then why not just go monochromatic?

monochromatic looks good to me

i have to admit the circles look kinda out of place through. rather than circles, what about checkered (alternating pixels) squares? wouldn't be grayscale, but wouldn't be black either

Wouldn't fit. The tiles are only 4x4px. The checker pattern would literally only consist of two black pixels in a / shape. Triangles can't be drawn in a 4x4px space for that matter, either. There is a very finite number of possible designs with such small blocks. I think I just used about half of them.

I think i would go with circles, filled circles, and squares.  The biggest issure you would have is making sure they don't blur together, and this way they all have some white in them