Four bugs that cost me 40 test games writing a tank bot for battle.training

Four bugs plagued a new tank bot in the battle.training arena, costing the author 40 test games before it was ready for the November Cup. The first issue was a swallowed exception causing matches to run to completion despite crashes. The solution involved wrapping the controller.tick(o) in a try-catch block and printing the first stack trace.

The second bug stemmed from positions, distances, and gun ranges being represented as fixed-point Q16.16 numbers, leading to inaccurate range checks that caused the bot to chase contacts across the map and leave itself vulnerable. The author discovered this by printing the raw range values from the rules object instead of relying on a markdown table.

Third, the single refusal pattern of "move:startup" orders during the opening ticks was due to the engine refusing movement orders under certain conditions. Wrapping the order in an if statement to check if the unit can move eliminated these refusals entirely. Lastly, the author found that implementing a draft strategy could yield significant wins without even firing shots.

By allocating points to an APC, MBT, and two scouts, the bot secured wins even when it never engaged in combat. This strategy proved particularly effective on certain maps, such as one with a wide river and forested center, but the author did not test other drafts. After addressing these four bugs, the bot achieved a 28-12 win record (70%) against the four house bots in local testing. The author then enrolled the bot in the promotedby.ai November Cup.