The player is constantly moving horizontally. How do i make him go up when space is pressed and down when space is not pressed.
Depends on how you are moving the player.
If you do it by increasing the X position of the player, then create a variable (say named yForce). Set yForce to -10 if space is pressed, and 10 if space isn’t pressed. When you update the X position of the player, also update the Y position by adding the value of the variable yForce.
However, you will get a more realistic movement if you use the Physics 2 behaviour. Apply a permanent force along the X axis for horizontal movement (use 0 degrees). Apply a instant force upwards (use -90 degrees) when space is pressed to go up. No need to worry about space not being pressed, as gravity will kick in and drop the player.
Platformer character Behavior with less gravity
Key pressed condition + “Allow jumping again” action