You can make objects move up, down or across the screen very easily.  This is particularly important for shooting games.

Before you can set up movement and shooting, you need to understand how the coordinate system in Game Maker works.

 

Where is it?

The game area and positions of objects in it are measured in pixels.  You can set the size of the game area in the room properties, but by default it is 640 pixels across and 480 down, measured from the top left hand corner.

Each object has an x and y variable that stores the coordinates of its position.  X is the distance across from the left hand side and y is the distance down from the top. You can use or change these variables to place objects in certain positions on the screen.

In Game Maker as you move your mouse around a room, you can see the coordinates of the point where your mouse is at the bottom left of the screen.

 

 

Here is a simple Game Maker 'game' that you can download that will show you what the coordinates of each point are.  

 

 

You can work out the coordinates of one point relative to another point whose coordinates are (x,y).  This activity should show you how it works.  (Ask someone else to help if you can't understand it.)

Try to guess the coordinates of each point, then click on a point with your mouse to see if your were correct.

Now you know where things are, you are ready to move on to shooting...