Migration Guide

Origins

Robocode Tank Royale was created by Flemming Nørnberg Larsen (fnl), the long-time maintainer of classic Robocode, to keep the same competitive game alive on a modern, language-agnostic engine.

A bot that took a season to tune in classic Robocode does not need a rewrite for Tank Royale. It needs a pass through a checklist, applied in an order that turns compiler errors into logic errors before logic errors turn into silent losses. Skip the order and a heading-sign bug can hide behind a dozen unrelated compile errors for an afternoon.

This guide assumes the bot already works in classic Robocode, and it does not repeat the individual differences: see API Changes for the renamed classes and methods, and Physics Differences for the angle, turn-sign, and hitbox changes.

1. Swap the base class first

Replace Robot, AdvancedRobot, or TeamRobot with Tank Royale's Bot interface, and fix every compile error that follows from renamed methods and events before touching any logic. This step alone typically finds most of the mechanical differences: execute() becomes go(), ScannedRobotEvent becomes ScannedBotEvent, and so on.

Do not "fix" a compile error by guessing a plausible Tank Royale name. Check it against the API Changes table, since a wrong guess that happens to compile is worse than an error that stops the build.

2. Fix the run() loop before anything else

Classic Robocode allows while (true) because the engine can kill the bot's thread outright. Tank Royale cannot do that safely, so its clients expose a running flag instead, isRunning() in Java and C#, self.running in Python. Change the loop condition immediately after the base class compiles, or the bot never terminates cleanly between rounds during testing.

3. Convert every heading and turn

This is the step most bugs hide in, because a heading-sign error still compiles and still moves the bot, just in the wrong direction. Search the bot for every angle computation: bearing to target, escape angles, movement headings, and convert each one using the formula from Physics Differences, $h_{TR} = (90 - h_C) \bmod 360$ . Also check the sign on every relative turn, since turning right decreases the heading in Tank Royale instead of increasing it.

A fast way to catch a leftover sign bug: run the ported bot against a stationary target and watch whether it turns to face the enemy or away from it. A movement or targeting bot that suddenly can't hit a still target almost always has one unconverted angle left.

4. Re-check hitbox-dependent math

Classic Robocode's 36×36 axis-aligned square and Tank Royale's 18-unit-radius circle agree closely head-on but differ at the corners. A bot that computes exact bullet shadows or GuessFactor bins against the classic square's corners will be slightly off in Tank Royale. Widen any hardcoded hit-tolerance margin rather than trying to model the exact geometry twice.

5. Rebuild team messages on the new limits

A ported TeamRobot that broadcasts freely can exceed Tank Royale's per-turn packet limits, where classic Robocode only capped message size. Batch or throttle any message loop that fires every turn, and read Team Communication & Coordination for the exact numbers before assuming the old protocol still fits.

6. Test in isolation, then in a real battle

Before running full battles, fire the ported bot at a wall-hugging or stationary opponent and confirm three things in order: the bot moves the direction it intends to, the gun tracks the right target, and it doesn't crash on the first onBotDeath or onRoundEnded event. Only then run it in RoboRumble-style battles, where a subtle heading bug shows up as a mysteriously low win rate rather than a crash.

Platform Difference

Tank Royale bots run as separate processes and can be skipped for a slow turn instead of finishing late like a classic Robocode thread. A bot that passes isolated testing but underperforms in full battles may simply be too slow per turn, not wrong.

What does not need porting

The strategy survives the move untouched. A wave surfing movement, a GuessFactor gun, or an anti-gravity swarm tactic reads the same battlefield and reasons about the same physics on both platforms. Only the vocabulary for reading that battlefield changes. A bot that wins on classic Robocode's RoboRumble should win on Tank Royale's leaderboard too, once the checklist above is clean.

Migration Guide ​

1. Swap the base class first ​

2. Fix the run() loop before anything else ​

3. Convert every heading and turn ​

4. Re-check hitbox-dependent math ​

5. Rebuild team messages on the new limits ​

6. Test in isolation, then in a real battle ​

What does not need porting ​

Further Reading ​