We continue to learn how to use Game Maker by working tutorials and tweaking the tutorial games a bit to explore Game Maker's capabilities. Here are some of the main points from yesterday.

1. The x-y coordinate system used by Game Maker for rooms is different from the standard coordinate system in that origin (0,0) is in the upper-left corner of the room and y values increase in the down direction.
   Source: Internet Programming with Java Course
2. The notion of depth is important. Larger numbers are more distant from the observer. Negative numbers are closer. (The main plane flies at a depth of -100, enemy planes and bullets (fired from the main plane) are at depth 0, while the islands are at depth 10,000.)
3. A variable holds the value of some property. A variable can belong to an object—for example, x, y, and can_shoot—or a variable can belong to the game—for example, score, room_width, and room_height.
4. The function random(x)computes a random real number between 0 and x. (The number is always smaller than x.) The function is useful for placing objects at random locations.
5. Sometimes it's useful to center a sprite at the center pixel of the graphic and sometimes it's useful to center it at the upper left corner (or other corner).
6. The concept of relative is important. Relative amounts are added to a variable's current value and the sum becomes the variable's [new] value. Non-relative (absolute) amounts are given as the value of a variable.
7. An object is a kind of thing in a game. An instance is a specific thing (occurrence of an object).
8. Instances don't necessarily have to be destroyed. They can be reused by moving them to another position in a room—for example, the way island instances scroll off the bottom and the way the clown instance jumps to a new location when clicked.
9. Collisions are between instances. Collision checking can be deactivated for some instances—for example, islands—to make a game run faster.
10. There are 30 steps in a second.

The main goal for today is to complete the scrolling shooter tutorial work and to implement the revised Catch the Clown game.

Work with your partner from yesterday.

1. Tutorial: Creating a Scrolling Shooter (zip file, 1.8 MB) Complete this tutorial, which we started yesterday. Work with a partner.
2. Implement the revised Catch the Clown game (from yesterday). When you are finished, play it and then demonstrate it to me. You can add other enhancements, such as
   • Obstacles in the room
   • Clown leaving a ghost that, when clicked on, subtracts from the score.
   • Clown periodically goes into hyperspeed mode and a click is worth more points.

Assignment

It would be good to find some resources on the Web that can be used in the games we will develop. Find three Web sites that have good sprite resources for download and three Web sites that have good background music and/or sound effect resources for download. These resources should not have copyrights. Please find interesting and useful resources. Please don't just use the first three that Google lists. We want to find a variety of resources that everyone in the class can draw from.

Send the six links to me via e-mail before the start of class tomorrow.