Presentation slides for a cell phone game currently in development.

1. Presenting “Unnamed Game”

2. Basic Mechanics
 Overhead space shooter
 Control ship with arrow keys
 Press fire button to fire all of your guns at once
 Cells
 break off as a ship takes damage
 enemies are built from cells
 must be directly hit to be destroyed
 You must protect your brain cell – if it takes 3 hits,
you’re dead!

3. Cell Types
 Basic Cell
 Does not shoot
 Provides cover for other cells
 Gun Cell
 Shoots a fast projectile in one direction
 Missile Cell
 Shoots a seeking missile
 Short lifespan
 Melee Cell
 Sword-like cell that must touch a cell to kill it

4. Behind the Scenes
 Multiple Child tree structure for ship
 Brain Cell is the root
 Hitting a cell destroys it, but releases children cells back
into environment
Can be retrieved by you or enemy

 Traversal used for most cell operations
Drawing

Shooting

Collision detection

Rotation and translation


5. Behind the Scenes
 Collision Detection
 Every bullet from every ship can collide with every other
ship
 Time-based collision needed with high projectile speeds
and small cell sizes
 Bounding circles used to minimize collision checks

6. Challenges Faced
 Mobile Game Development
 Pros:
Easy to get started

Java-based

Netbeans Game Development tools

 Cons:
Little memory (~1-4 MB heap size)

Small screen

Awkward controls

Not completely portable among J2ME phones


7. Challenges Faced
 No floating point arithmetic
 Floating point math is not on all J2ME phones
 Used an open-source fixed-point library
 We use 64-bit fixed-point longs
With 32-bit we did not have enough precision or range


8. Memory
 Use of the new keyword was expressly forbidden
without a good reason to back it up
 Operations on vectors to avoid allocating memory
 Pair a plus with a minus
 Pair a multiply with a divide
 Minimize vector normalization (slow)
 Garbage collection is actually reasonably fast, but we
still want to avoid using it

9. Challenges Faced
 Management
 Team members have other priorities (school work, jobs,
etc.)
Long term goals are ineffective

 Members come and go
 Code in small pieces to avoid losing work when a member
leaves
 Short jamming sessions more effective
 Declare goals to reach at the end of a 5 – 10 hour session
 Fosters team atmosphere
 Peer coding helps members become familiar with code

10. Bugs and Hax

11. Bugs
 Can keep up with your
own bullets
 Phantom ship

12. Hax
 The fixed-point arctan2 function has a bug
 Good solution – do some math and checks to
compensate
 Bad solution – reorder the sprite rotation array so that
the rotation works anyway
 Guess which one we did?

13. Future Plans
 Improve collision detection (esp. for melee cells)
 Work on single-player experience
 Tighten up the graphics on level 3…I mean, import the
rest of the sprites and get a background
 Multiplayer over Bluetooth
 Port to Flash (better graphics, online multiplayer)