Pretty cool tool that I will definitely recommend to people asking me about making a platformer, but it's got a few issues.
1. The rate of deceleration when you let go of the control pad and when you press the opposite direction you're travelling are always the same. Both on the ground an in the air. This means any low acceleration setting will always feel like the player lacks control when trying to turn around; either actively trying to stop or coasting to a stop will feel wrong no matter the settings. This also means there is no way to have zero momentum decay in the air but retain the ability to turn around or stop mid-air, making Mario and Sonic like controls impossible to replicate.
2. Air Control and Air Brake are separate settings, but from a game feel perspective they are the same thing: how fast the player accelerates while in the air. This creates a weird swing in momentum when turning around mid-air if braking is slower than accelerating, which makes precision impossible. It's weird to have these separate when there is no distinction between no d-pad input and actively trying to turn around.
3. You can't make down gravity less than up gravity. I can't think of a game that does this, but we should have the option.
4. Rounded corners for collision makes the player slip off when standing on a ledge. A better solution is to slightly narrow the hitbox. Platformer player hitboxes are almost never as big as the graphic for the player.
5. This isn't really an issue one can fix, but I feel is worth mentioning. The game teaches how to tailor platformer physics to level design, when in practice it's always done the other way around. You develop satisfying physics, then design levels suited to those physics. It's out of the scope of this project, but a level editor would better replicate the real world experience of making a platformer.
6. The run & jump presets for Mario and Sonic feel way off. Probably because of issue 1. "Sonic" coming to a stop in the air is especially jarring, unless you were going for Sonic the Hedgehog 4.