Here is the next Billy Hatcher GBA minigame. It's Chu Chu Rocket Challenge. This simple puzzle game packs over a dozen challenges to play with and with it, plenty of play time. Watch me play it below. I had already gotten the hang of it by this time, fortunately.
The premise is quite simple: the player sets directional cursors to move either mice or cats. You can be tasked with moving mice to the goal or letting cats eat them. There are also soccer challenges where you play against the computer. Unfortunately, the computer is really fast so the main strategy is to play slow and with a fixed goal because you can't outrun the computer. And spoilers, the final map is super-easy. Compared to the last few maps, it's a huge difficulty dive.
This time, GM showed me how to convert it to a bootable GBA ROM. When I find the next mini-game, I'll get to show it sooner.
Finally, some pics of the game below. Spoilers, too.