thing about the double jump is i have no idea how to make it always boost the player to the same height. for example, if you were to press double jump like millisecond after you jumped, it would rocket you into the sky. if you were to double jump right before hitting the ground, you would stay in the air for maybe 0.2 seconds longer instead of jumping up at all. so I made that you have to time it.
edit: unless I could make it be more of an upwards dash. then it would always work because then it would teleport you into the air. could be an easy solution but then the player could do stuff like clip through walls and then id have to practically re-create the entire game.