Computer Science Canada :: View topic - Simple gravity program

var x, y, jump : int
var key : array char of boolean
setscreen ("graphics")
x := 10
y := 50
procedure draw
drawoval (x, y, 10, 10, black)
drawline (x, y - 10, x, y - 30, black)
drawline (x, y - 30, x - 10, y - 40, black)
drawline (x, y - 30, x + 10, y - 40, black)
drawline (x - 10, y - 20, x + 10, y - 20, black)
drawline (1, 10, maxx, 10, black)
end draw
draw
loop
Input.KeyDown (key)
if key ('w') then
jump := 32
for i : 1 .. 5
jump := jump div 2
y := y + jump
delay (50)
cls
draw
end for
y := y + 1
jump := 1
for i : 1 .. 4
jump := jump * 2
y := y - jump
delay (50)
cls
draw
if i = 4 then
y := y - 2
cls
draw
end if
end for
end if
if key ('d') then
x := x + 5
delay (50)
cls
draw
end if
if key ('a') then
x := x - 5
delay (50)
cls
draw
end if
end loop

Author:	Cervantes [ Thu Oct 19, 2006 9:53 pm ]
Post subject:
A good try, but it's fundamentally wrong. You should not have for loops within those if statements. Why? Because if you put a for loop in there, the execution will remain in there while the character moves and no other part of your program will run. It's like this: "You want to move a step to the right? Sure, but doing so will prevent your enemies or allies from moving." Instead, you need to create variables that store the velocity of your character. If you hit the up arrow and you're on the ground, set the y velocity to some value, say 5. Then while you're in the air, decrease the y velocity by some constant value with every iteration of the loop. That's acceletaion at work.