Game Dev From Zero · Episode 9

Jump lab

Gravity pulls a little every frame. A jump pushes a lot, once. Jump around, then change the numbers, and find out why a jump asks "was it pressed?" and not "is it held?".

The game ← → / A D move · Space / W / ↑ jump · R reset

Top row: jump is held (a state). Bottom row: jump was pressed (an event: one frame). Newest on the right.

velocity.y
0
on_ground
true
jump height
0 px
time in the air
0.00 s

The code lit = running now


    

  


  

    

      
The numbers

      

      
      
      
      
jump if the key…
        

      
on_ground check
        

      
"fall faster" multiplies gravity while you're falling. With these numbers a jump goes
        48 px high, 0.80 s in the air.

      

    


    

      
Things to try

      
    
        
  1. Switch to is held and hold the jump key down. Boing, boing, boing…
    2. 
        
  2. Turn the on_ground check off and mash jump. How high can you climb?
    3. 
        
  3. Set fall faster to 2. Does the jump feel better or worse?
    4. 
        
  4. Try Moon. Then make a jump that's just as high, but quick.
    5. 
        
  5. Set gravity to 0 and jump. Bye! (Press R to bring the ghost back.)
    6.