Poseidon: Alt Ctrl, specifically the melon level, has you moving your ship up and down the screen by filling up buckets of water.
You see, this game is controlled by two actual buckets of water. You are given two cups that you can use to move water between these two buckets. When the left bucket is full, your boat is at the top of the screen, and when it is less full, your boat will fall.
Your goal is to collect watermelon seeds that are on the screen by moving up and down into these different waves. There are also flamingos inside that water, looking to hit and hurt your ship, which you need to float away from. The specific level that was showcased at Bemyhuman was colorful and looked like it belonged inside a watermelon.
Moving water from one bucket to the other made the game hectic and challenging, as it took quite a bit of water to move the boat up or down, so you needed to be quick to get the most seeds.
Posiedon: Alt Ctrl is a really wonderful idea with a great controller for a simple concept.
You can grab more information on Poseidon: Alt Ctrl on Itch.io.