Creating Mario-Like Game, Need Help

[FearSonic]

I'm creating a Mario-like platformer game, and I'm having trouble having gravity implemented. I'm moving things around using Input.KeyDown, and using whatdotcolour for collision detection, since I don't know any other way. I just have a few questions:

1) How do I put gravity in, if my code is somewhat like this:

code:

loop     setscreen ("offscreenonly")     Draw.FillBox (0, 0, maxx, maxy, 255)     Draw.FillBox (400, 200, 500, 300, 0)     Draw.FillOval (ballx, bally, 10, 10, 0)     Input.KeyDown (chars)     if chars (KEY_UP_ARROW) then         bally := bally + 1     elsif chars (KEY_DOWN_ARROW) then         bally := bally - 1     elsif chars (KEY_LEFT_ARROW) then         ballx := ballx - 1     elsif chars (KEY_RIGHT_ARROW) then         ballx := ballx + 1     end if     if bally + 10 >= maxy then         bally := bally - 1     elsif ballx + 10 >= maxx then         ballx := ballx - 1     elsif bally - 10 <= 0 then         bally := bally + 1     elsif ballx - 10 <= 0 then         ballx := ballx + 1     end if     if whatdotcolor (ballx + 11, bally) = 0 and chars (KEY_RIGHT_ARROW) then         ballx := ballx - 1     elsif whatdotcolor (ballx - 11, bally) = 0 and chars (KEY_LEFT_ARROW) then         ballx := ballx + 1     elsif whatdotcolor (ballx, bally + 11) = 0 and chars (KEY_UP_ARROW) then         bally := bally - 1     elsif whatdotcolor (ballx, bally - 11) = 0 and chars (KEY_DOWN_ARROW) then         bally := bally + 1     end if     colorback (255)     View.Update end loop

2) Is there another way to implement collision detection using a more efficient way? I found that if I didn't use the elsif with the 'and' operator, that it would work on one side, but not on the other.

3) How do I implement sprites? I've looked at Dan's Sprite program, but it was WAYYY too confusing for me.

Thanks in advance! It's for my Grade 10 Computer Science ISU!

[FearSonic]

Also, I'm wondering if I can make the ball go in a diagonal direction, I tired using:

code:

if chars (KEY_UP_ARROW) and chars (KEY_LEFT_ARROW) then x := x - 1 y := y + 1 end if

And it doesn't work, any suggestions?

[Tony]

gravity is acceleration. It is applied to unit's velocity variable. When unit is in the air, each time though the loop, gravity (usually negative) is applied to the velocity and velocity moves the unit in the direction.

When you first jump, velocity is set to a positive value and unit begins to rise up, but as gravity reduces the value of the velocity, unit slows down and eventually stops (that is the highest point of the jump). At that point unit begins to fall down, picking up speed as gravity turns velocity variable into a negative value.

As for sprites, it's ether Sprite module in v3.1 or DanSprite in v4.* Which are preaty much the same. DanSprite is not complicated. You don't have to understand the coding behind it, just use methods exported (same way as you don't have to understand how Draw.Box works)

[FearSonic]

Thanks Tony! Would you happen to have an equation for gravity that would work? The other equations I've seen were all conflicting, and I couldn't tell which to use!

[Tony]

code:

const gravity:int := -1 var velocity:int := 25 var y:int := 0 var x:int := 100 for i:1..100 velocity += gravity y += velocity Draw.FillOval(i,y,5,5,red) delay(100) if y<0 then exit end if end for

[FearSonic]

Thanks again Tony! I tried implementing it so that it did it everytime I pressed the Up arrow, but it doesn't work for some reason. Heres the code:

code:

if chars (KEY_UP_ARROW) then         for i : ballx .. ballx + 20             velocity += gravity             bally += velocity             Draw.FillOval (i, bally, 10, 10, 0)             delay (100)             if bally < x then                 exit             end if         end for     end if

[FearSonic]

I changed up your program a bit, so instead of just going up and going straight down, I made it kinda bounce going lower and lower. It isn't the correct physics, but hey it's a start.

code:

const gravity : int := -1 var y : int := 10 var v : int := 30 var velocity : int := v loop     Input.KeyDown (chars)     if chars (KEY_UP_ARROW) then         for i : 50 .. maxx             velocity += gravity             y += velocity             Draw.FillOval (i, y, 10, 10, red)             delay (20)             Draw.FillOval (i, y, 10, 10, 0)             if y < 0 then                 velocity := v - 5                 v := v - 5                 y := 10             end if             View.Update         end for     end if end loop

My only problem now is implementing it into the game!

[the_short1]

man... if i had known it was this simple...

also now they i have finished physics in science... it makes more sense... hehehe


nice code there tony..... im sure itll come in handy eventually.... so i saved to HD.,