Collisions with a platform

[Adaub7282]

Turing:

%Constants const gravity :int := 2 %Variables var x := 20 var y := 20 var y_velocity := 0 var keys : array char of boolean var platx1, platx2, platy1, platy2 : int platx1 := 100 platy1 := 20 platx2 := 300 platy2 := 30 %Graphics View.Set("offscreenonly") %Loop loop     Input.KeyDown  (keys)     if keys (KEY_UP_ARROW) and y <=20 then %jump         y_velocity := 30     end if     if keys (KEY_LEFT_ARROW) and x > 0 then %move left         x -= 5     end if     if keys (KEY_RIGHT_ARROW) and x < maxx then%move right         x += 5     end if         if y = platy2 and x >= platx1 and x <= platx2 then %attempt at making the red platform solid         y := 40         y_velocity := 0     end if             y_velocity -= gravity %making gravity relevant     y += y_velocity %making y_velocity relevant     if y <= 20 then %making the ground solid         y := 20         y_velocity := 0     end if         Draw.FillOval (x, y, 10, 10, blue) %player     Draw.FillBox (0, 0, maxx, 10, green) %ground     Draw.FillBox (platx1, platy1, platx2, platy2, red) %platform     View.Update     delay (20)     cls end loop

Alright, the above code is an attempt at a simple program. All it is supposed to do is have a moveable ball, that can jump and land on a platform. The platform, however, is still not "solid" and the ball passes through. I have read through my code several times and can't find out what I have done wrong. Help would be much appreciated. On a side note, how do I make the screen move with the character? Example: Mario for the NES.

[Scott]

Your math is making the ball jump through the platform. See your ball is moving 2 at a time, that way it passes right through the 1 pixel you are checking for..
Instead of

code:

y = platy2

try

code:

y <= platy2 and y >= platy1

That way it will stop if it passes through your 10 pixel thick platform, not just the 1 pixel thick surface. With this you are stopping and the ball will be half in the platform, try and make it so the ball stops when its edges hit to make up for the help we gave you. Good luck

edit : better explanation.

[Adaub7282]

Thank you, I wasn't sure if it would still pass throught the correct pixel, it would just spend 1/2 the time at that pixel then if gravity were set to 1.