NaaLaa

Hi, I have a few more questions.
How can I apply gravity to a character so that it stops when it touches the ground? And how can I make the character jump when I press a key?

Hi, there is a good example from Marcus in the examples folder of n7, which is worth a look in my view:
"examples\games\jumping_on_lines.exe"

Hope this helps - Kevin.

Here's a simpler example than jumping_on_lines, just ask if something is unclear


Edit: When I write platform games I usually give less "air control" than here, because it's pretty difficult (in reality) to change direction in the air while jumping

Here I replace the ground with a list of rectangles. This code is dumb and not optimized. But I do the collision against rectangles in a different (but very clumsy here) way than someone posted in another thread. I prefer not to look at the player's movement to decide where to put him, instead I push the player out of a rectangle in the direction (left, right, up or down) that causes the smallest offset. This would function better when dealing with moving obstacles.

(01-27-2026, 05:40 PM)Marcus Wrote: [ -> ]Here's a simpler example than jumping_on_lines, just ask if something is unclear

Code:

' Gravity.

set window "Gravity", 256, 240, false, 3
set redraw off

' Player position.
playerX = 152
playerY = 0
' Size.
playerW = 16
playerH = 24
' Speed.
playerDX = 0
playerDY = 0
playerOnGround = false

' Ground.
groundY = 208

' Game loop, quit with escape key.
while not keydown(KEY_ESCAPE, true)
    ' Increase speed left/right on key left/right or decrease speed if left/right isn't pressed.
    if keydown(KEY_LEFT)        playerDX = max(playerDX - 0.1, -2)
    elseif keydown(KEY_RIGHT)   playerDX = min(playerDX + 0.1, 2)
    elseif playerDX < 0         playerDX = min(playerDX + 0.2, 0)
    elseif playerDX > 0         playerDX = max(playerDX - 0.2, 0)
   
    ' Is player on ground?
    if playerOnGround
        ' Does player want to jump?
        if keydown(KEY_UP, true)
            ' Set players vertical speed to -3 and set playerOnGround to false.
            playerDY = -3
            playerOnGround = false
        endif
    ' Player is in air.
    else
        ' Check if player has hit the ground.
        if playerY + playerH >= groundY
            playerOnGround = true
            playerY = groundY - playerH
            playerDY = 0
        ' Increase vertical speed, this is gravity!
        else
            playerDY = playerDY + 0.1
        endif
    endif
   
    ' Move player.
    playerX = playerX + playerDX
    playerY = playerY + playerDY
   
    ' Draw background.
    set color 0, 0, 0
    cls
    ' Ground.
    set color 192, 128, 0
    draw rect 0, groundY, 320, 8, true
    ' Player.
    set color 255, 200, 0
    draw rect playerX, playerY, playerW, playerH, true
   
    redraw
    fwait 60
wend

Edit:  When I write platform games I usually give less "air control" than here, because it's pretty difficult (in reality) to change direction in the air while jumping

Thanks for the example, Marcus. Let's continue working on this example, which is simpler than the second one. For now, I don't want to use lists of objects to avoid complicating the code and to make it easier to understand.

How about showing me a second example, but without using the min and max functions so it's easier to understand? And if possible, use the collision function between rectangles to make the example clearer.

function collision_rect(x1,y1,w1,h1,x2,y2,w2,h2)

return x1 + w1 > x2 and x1 < x2 + w2 and

y1 + h1 > y2 and y1 < y2 + h2
endfunc

Another thing you could add to show how it's done is a solid platform that the player can't cross from anywhere, and another platform that can be crossed from below by jumping up.

In other words, a floor and two platforms, without any lists to make it easier to read.

Okay

But I'm keeping the 'min' and 'max' calls, because they reduce the number of 'if' statements so much. They're very simple to use. 'min' returns the smallest of two values, and 'max' returns the largest. I rewrote the push-one-rect-out-from-another a bit.

Thanks Marcus, now it's time to study it calmly.

I'll continue with other questions in another thread so as not to complicate this one further.

Perhaps it would be a good idea to create a small physics library to facilitate the development of this type of game.