GMnet - Manual

5. Setting up the basic platformer

We now need to create a simple platformer. Since this is not supposed to be a tutorial on platformers, and the platformer we are going to use is simple and pretty bad, simply follow the instructions and copy the code.

1. Setup our game room

Give the game room htme_rom_demo we created a nice background color and the dimensions 800x600. For this demo, we are not going to use views.

2. Create a wall

Create a solid object, called htme_obj_wall. Give it the sprite htme_spr_wall. This is our new wall. Place it into the game room, build some walls, a floor and maybe some platforms.

3. Create the player object

Next we are going to create our player.

Create the object htme_obj_player and give it the sprite htme_spr_player.

Into the create-Event put the following code:

///Setup basic stuff for the demo platformer.
self.pressed_jump = false;
self.pressed_left = false;
self.pressed_right = false;
self.name = "";

/** Totro generates random names and is not part of the main engine, it's
  * another marketplace asset by me :)
  */
var ttr = totro(5,7,1);
self.name = ttr[0];
/** Gives this player a random color. */
self.image_blend = irandom(16777215);
}

The self.pressed... variables will store if our player pressed the buttons to move or to jump. We need to store this in a variable as a preperation for later, when we want to add the player to the engine. But you'll see :).

Into the step event put the following code:

///Perform platforming!
//This is a very basic example of a platformer. You should not program your physics like this!

if (place_free(x, y+1)) {
   gravity = 0.2;
} else {
   gravity = 0;
   vspeed = 0;
}

self.pressed_jump = keyboard_check(vk_space);
self.pressed_left = keyboard_check(vk_left);
self.pressed_right = keyboard_check(vk_right);

if (self.pressed_jump && (!vspeed)) {
    vspeed = -12
    image_xscale = 1;
    image_angle = 90;
}
if (self.pressed_right) {
    x+=10;
    image_xscale = 1;
    image_angle = 0;
}
if (self.pressed_left) {
    x-=10;
    image_xscale = -1;
    image_angle = 0;
}
if (vspeed < 0) vspeed=vspeed+gravity;

As you can see, we currently just put the button presses into the variables self.pressed... and check them. We will change that later.

Now create a Collision with htme_obj_wall event and put the following code in it:

///Set speed to 0 when hitting a top wall
if (!place_free(x, y-16)) {
    move_contact_solid(90,-1);
    vspeed = 0;
}

if (!place_free(x, y+16)) {
   move_contact_solid(270,-1);
   gravity = 0;
   vspeed = 0;
}

Into the draw event, we will put some code to draw the name we randomly generated in the create event. First put "draw self"" into the event and then this code:

///Draw nameplate
draw_set_color(image_blend);
draw_set_halign(fa_center);
draw_text(x,y-sprite_yoffset-5-string_height(self.name),self.name);
draw_set_halign(fa_left);
draw_set_color(c_white);

Basic platformer: Done!

4. Test

Start the game and then start the server. You can now test out how bad the platformer really is. But hey, it does the job. The next tutorial is actually related to the engine again.

How it should look like