if you are talking about collision and gravity, then it isn't too hard for some basic gravity. heres a outlie:
make a velocity variable for the player and a constant variable that will be your gravity force.
next every loop add the gravity force to the velocity variable. then check for collision with the ground.
if there is collision set the velocity to 0
if there isn't collision then add the velocity to the player Y variable(but don't set it to zero).
Your velocity and gravity should probably be floats.
That's all there is to it!
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