Somewhat complicated request, I don't expect this to be done

[RaccAttacc]

Alright, so I'm making a episode staring a Koopa Troopa. (Over Mario)
My idea is when moving at top speed, when the player crouches. They will turn into a Koopa Shell.

So here's my idea- I said that twice. Um. Is the player would turn into a spinning turtle shell when they crouched. And obviously different colors based on the power-up they were wearing.
So like, 6 custom NPCs are needed? Because I don't want the player to have this ability when they're small.
Obviously they can jump.

Again I don't expect this to be done, but I'm just putting it out there incase someone has some time on their hand, and is really bored.
Thanks for reading.

[Emral]

From the sound of it you need 0 NPCs, collision checks against breakable blocks and npcs, and some extra frames on your player spritesheet.
What you'd basically do is detect ducking state at maximum speed and toggle a flag in your own code that enables your own shell-like physics. You definitely wouldn't want to use NPCs because with NPCs you could basically kill yourself by shelling into another shell or any thrown NPC.

Just as a brief outline for how this would be done by whomever interested.

[RaccAttacc]

From the sound of it you need 0 NPCs, collision checks against breakable blocks and npcs, and some extra frames on your player spritesheet.
What you'd basically do is detect ducking state at maximum speed and toggle a flag in your own code that enables your own shell-like physics. You definitely wouldn't want to use NPCs because with NPCs you could basically kill yourself by shelling into another shell or any thrown NPC.

Just as a brief outline for how this would be done by whomever interested.

Thank you so much, I didn't even think of this