1

🧱

Player, Wall & the Grid

Set up obj_player, obj_wall and a test room

Active

🎯

Goal for this step

Create the player and solid wall objects and lay out a room.

1New project. Sprites: spr_player (32×48, orange) and spr_wall (32×32, green). Objects: obj_player, obj_wall.
2IMPORTANT: on spr_player set the origin to Middle Centre, collision maths gets much saner.
3In the room editor, enable grid snap 32 and paint a floor plus some ledges from obj_wall instances.
4Create event of obj_player: the movement variables below. No motion yet, foundations first.

obj_player · Create

move_speed = 4;
jump_force  = -11;
grav        = 0.5;
vsp = 0;    // vertical speed
hsp = 0;    // horizontal speed

✏️

Fill in the Blanks

+15 XP

Solid level pieces are instances of obj_. The sprite is set to Middle Centre so position maths stays simple. Room grid snapping was set to .

🧠

Knowledge Check

+15 XP

Why do we use OUR OWN hsp/vsp instead of the built-in hspeed/vspeed here?

AThe built-ins are broken

BWe need to test collisions BEFORE applying movement, manual variables give us that control

CThey are faster to type

2

🚶

place_meeting Movement

The most famous 10 lines in GameMaker

Locked

🎯

Goal for this step

Implement collision-safe horizontal and vertical movement.

1place_meeting(x, y, obj) asks: "if I stood at this position, would I overlap that object?", collision BEFORE moving. This is GameMaker’s crown jewel.
2The pattern: compute hsp from input; if the spot ahead is blocked, inch up to the wall pixel-by-pixel then zero the speed; else move.
3Same for vertical with gravity added to vsp first.
4This exact Step code is in thousands of shipped games. Learn it by heart.

obj_player · Step

var key_left  = keyboard_check(vk_left);
var key_right = keyboard_check(vk_right);
hsp = (key_right - key_left) * move_speed;
vsp += grav;

// horizontal
if (place_meeting(x + hsp, y, obj_wall)) {
    while (!place_meeting(x + sign(hsp), y, obj_wall)) x += sign(hsp);
    hsp = 0;
}
x += hsp;

// vertical
if (place_meeting(x, y + vsp, obj_wall)) {
    while (!place_meeting(x, y + sign(vsp), obj_wall)) y += sign(vsp);
    vsp = 0;
}
y += vsp;

⌨️

Code Challenge

+20 XP

Complete the pixel-perfect horizontal block:

obj_player · Step

if ((x + hsp, y, obj_wall)) {
    while (!place_meeting(x + (hsp), y, obj_wall)) x += sign(hsp);
    hsp = ;
}

💡 Hint: The look-ahead test; then creep one pixel at a time in the movement direction until flush; then stop.

🧠

Knowledge Check

+15 XP

The while-loop that inches toward the wall gives you…

ASlower movement

BPixel-perfect landing flush against walls, no gaps, no overlaps, at any speed

CWall destruction

3

🦘

Jumping & Coyote Time

Grounded checks plus the forgiveness timer

Locked

🎯

Goal for this step

Add jumping with the pro-level coyote-time polish.

1Grounded test: place_meeting(x, y + 1, obj_wall), is there floor one pixel below?
2Track coyote frames: reset to 6 when grounded, count down in air; jump allowed while > 0.
3(6 frames = 0.1 s at 60 fps, the same window you built in C++. Same design, new engine.)
4Also add jump buffering: remember a jump press for 6 frames so pressing JUST before landing still jumps. The two timers together = jumps that feel psychic.

obj_player · Step (additions)

var on_ground = place_meeting(x, y + 1, obj_wall);
if (on_ground) coyote = 6; else coyote--;

if (keyboard_check_pressed(vk_space)) buffer = 6; else buffer--;

if (buffer > 0 && coyote > 0) {
    vsp = jump_force;
    coyote = 0;
    buffer = 0;
}

✏️

Fill in the Blanks

+15 XP

The grounded check looks one pixel the player. Coyote time forgives late jumps; jump forgives early ones. Both timers run about frames.

🧠

Knowledge Check

+15 XP

Jump buffering handles the case where the player presses jump…

ATwice quickly

BSlightly BEFORE landing, the press is remembered and fires on touchdown instead of being eaten

CWhile paused

4

🎥

Camera & A Bigger World

Viewports that follow the player smoothly

Locked

🎯

Goal for this step

Expand the room and set up a smooth-follow camera.

1Resize the room to 2400×500 and build a longer level.
2Room editor → Viewports: enable Viewport 0, camera 800×500.
3Smooth-follow beats hard-lock: lerp the camera toward the player each Step in obj_game.
4lerp(a, b, 0.1) moves a tenth of the way per frame, smooth chase, no snapping. Clamp inside the room.

obj_game · Step

var cam = view_camera[0];
var cx = camera_get_view_x(cam);
var target = clamp(obj_player.x - 400, 0, room_width - 800);
camera_set_view_pos(cam, lerp(cx, target, 0.1),
                    camera_get_view_y(cam));

⌨️

Code Challenge

+20 XP

Smooth-follow the player:

obj_game · Step

var target = clamp(obj_player.x - , 0, room_width - 800);
camera_set_view_pos(cam, (cx, target, 0.1), camera_get_view_y(cam));

💡 Hint: Centre an 800-wide view on the player; the smoothing function blends a fraction toward the target each frame.

🧠

Knowledge Check

+15 XP

lerp(cx, target, 0.1) each frame produces…

AInstant snapping

BAn easing chase, fast when far, gentle when close, like a cameraman

CA shaking camera

5

🪙

Coins, Spikes & Respawn

Pickups and hazards, GameMaker style

Locked

🎯

Goal for this step

Add collectable coins and deadly spikes with a respawn.

1obj_coin: gold sprite; a Collision event with obj_player runs instance_destroy() and global.coins++, pickups in two lines!
2obj_spike: red triangle sprite; its collision with the player moves the player to global respawn coordinates.
3Store the respawn in obj_game create (global.rx / global.ry), draw coin count in Draw GUI.
4Feel the engine difference: what took loops and lists in Python is one visual event here, engines trade control for speed.

obj_coin · Collision with obj_player

global.coins += 1;
instance_destroy();

// obj_spike · Collision with obj_player:
other.x = global.rx;
other.y = global.ry;
other.vsp = 0;

✏️

Fill in the Blanks

+15 XP

A pickup deletes itself with (). Inside the spike’s collision event, refers to the player who touched it.

🧠

Knowledge Check

+15 XP

In obj_spike’s collision event, why is the player "other"?

APlayers are always other

BThe event belongs to the spike, self is the spike, other is whoever collided with it

CA GML quirk

6

🚩

The Goal & Multiple Rooms

Level exits, room flow and the finish line

Locked

🎯

Goal for this step

Add a goal flag that advances rooms, and finish the game.

1obj_flag: collision with the player → room_goto_next(), GameMaker rooms ARE your level system, built in.
2Build rm_level2 (copy rm_level1, redesign). Order rooms in the asset browser, that IS the level order.
3Last room: rm_win with a victory object (coins collected, R to restart via room_goto(rm_level1) + reset globals).
4Set global.rx/ry per room in a Room Start event so respawns follow the level.
5Two-level platformer with camera, coins, hazards: shipped. Episode 3 goes arcade!

obj_flag · Collision with obj_player

if (room != room_last) {
    room_goto_next();
} else {
    room_goto(rm_win);
}

✏️

Fill in the Blanks

+15 XP

Advancing a level is one call: (). The room order in the asset defines the level order.

🧠

Knowledge Check

+15 XP

GameMaker rooms map naturally onto…

ASave files

BLevels/screens, the engine gives you a level system for free where other tools needed load functions

CSprites

Run & Jump!GML Platformer

Run & Jump!
GML Platformer