Introduction
Learning and practicing new computer skills (a programming language, an IDE, an operating system, etc.) is a task that is often frustrating at best and intimidating at worst, especially when one is having trouble learning the system at its most basic levels. The philosophy of code katas, a form of practice with a name borrowed from Japanese martial arts, seeks to break the learning process down into a series of repeated drills, each one slightly more complex than the last. As the developer completes each drill, he or she gains essential skills along the way. This kind of "effortful practice" produces results faster than unfocused practice because it is focused around specific tasks, ideally just beyond one's current level of competence.
With this in mind, I set out to complete thirteen code katas for the Robocode API:
- Position01: The minimal robot. Does absolutely nothing at all.
- Position02: Move forward a total of 100 pixels per turn. When you hit a wall, reverse direction.
- Position03: Each turn, move forward a total of N pixels per turn, then turn right. N is initialized to 15, and increases by 15 per turn.
- Position04: Move to the center of the playing field, spin around in a circle, and stop.
- Position05: Move to the upper right corner. Then move to the lower left corner. Then move to the upper left corner. Then move to the lower right corner.
- Position06: Move to the center, then move in a circle with a radius of approximately 100 pixels, ending up where you started.
- Follow01: Pick one enemy and follow them.
- Follow02: Pick one enemy and follow them, but stop if your robot gets within 50 pixels of them.
- Follow03: Each turn, Find the closest enemy, and move in the opposite direction by 100 pixels, then stop.
- Boom01: Sit still. Rotate gun. When it is pointing at an enemy, fire.
- Boom02: Sit still. Pick one enemy. Only fire your gun when it is pointing at the chosen enemy.
- Boom03: Sit still. Rotate gun. When it is pointing at an enemy, use bullet power proportional to the distance of the enemy from you. The farther away the enemy, the less power your bullet should use (since far targets increase the odds that the bullet will miss).
- Boom04: Sit still. Pick one enemy and attempt to track it with your gun. In other words, try to have your gun always pointing at that enemy. Don't fire (you don't want to kill it).
The Robocode project, once managed by IBM and now an open-source, community-driven effort, provides a way to program armed virtual robots and pit them against each other. Robocode robots are controlled by programming three types of behavior: movement, radar scanning, and firing. Though the core concepts are simple, the API is versatile enough that in the hands of experienced developers, Robocode battles can become a serious business indeed.
Look at this genetic algorithm, now look back at mine. Sadly, my code lacks complex algorithms. But the idea behind the code katas is that, with practice, that code is what my code could look like. Each group of katas emphasized a specific skill, whether finding specific points on a map, circling a particular area, tracking and picking targets from among multiple enemies, or controlling the power of the robot's shots based on information acquired about enemy robots.
The first three position methods were easy to implement. The fourth took a little more work, but finding the center was fairly easy after writing methods to calculate the angle between the robot and the center, and the distance of the straightest path to the center, and the sixth was just a variation of the fourth. The fifth method was the hardest of the group for me, and it took a while before I realized that it was returning the wrong angles because the robot was not accounting for its own previous turning when calculating the turn angle. I made heavy use of the Math.atan2 method here, as it was easy to retrieve the x- and y-distances between two points for use in calculating the angle.
The Follow robots were easier to write, since most of the data needed to match the headings of enemy robots could be obtained from pre-made methods, especially the method which retrieves a scanned robot's name for easy tracking. Follow03 was easily implemented by causing the robot to scan continuously for enemies, store their data, and compare the results after each scan.
Most of the Boom robots were also quickly written; Boom01 and 03 only needed to fire automatically. Boom02 was also easily handled using the getName() function. I am still not sure whether or not I implemented Boom04 correctly; it lost its "lock" on the target frequently,
and occasionally aimed in the opposite direction of its target's motion. The problem was probably related to correcting for differences between the gun angle and the robot's heading, something I did not quite get the hang of; since each exercise in a group was based on previous ones, Boom05 could be the exercise where sloppily designed but still previously workable methods finally became unusable.
Overall, the "code katas" were easy ways to pick up basic programming skills, and even some of the errors along the way pointed the way to competitive strategies I might be able to use in the future.
