i like that there is no time pressure. i can analyze the board and think before i move. in comparison your first game is frustrating. it makes sense of course, but it's way to fast for me, and not relaxing. this is a relaxing puzzle.
i would change the mechanic of the red squares. as it is they work just like no squares. as falling down kills you too. how about it kills you if you touch a red square and a white (or green) square together, or a red square and empty space? that means you could use a red square only if the block is safely placed over it.
then you could introduce multiple colors that do different things. say, yellow shifts your block by one square. blue rotates it, purple makes it jump to a another purple block, another doubles one or all dimensions of the block, making it faster to move or able to cross larger gaps, one color could add or remove squares, changing the layout of the board, or move the target. etc...
since your goal is to learn 3d, each of these could have a different kind of 3d effect.
(btw: i made it in 303 moves)