Ricochet Robot is a great game by Alex Randolph. In it you move robots around, bouncing them off each other to reach various goals. Lunar Lockout and Pete’s Pike are two puzzles with similar gameplay created by Hiroshi Yamamoto. The only difference between them is that Ricochet Robot has a wall surrounding the outside edge of the board and internal barriers.
This puzzle is similar to both, but the pieces are bigger relative to the grid they travel on (2×2). The goal is to get one of them to cover the center square, marked in orange. Here is a simple puzzle:
For those who haven’t tried the previous puzzle/games, the green pieces can only move left-right/up-down, and once they start moving they can’t stop until they hit another piece. You are disallowed from losing any pieces off the edge of the board. So for example, the piece in the lower left can’t start by moving up; he would go straight up and off the board. Likewise the piece overlapping the goal can’t move at all initially; left, right, up or down, there is nothing to block him.
Here is a slightly more difficult puzzle:
Here’s another medium one:
I think perhaps the board needs to be larger to create really difficult puzzles, but I just read that Lunar Lockout started with a much larger board, but they eventually figured out how to create much more difficult puzzles on just a 5×5 board, so I’m going to keep trying with this board size for a bit. I’d appreciate any feedback on how hard these three are.