Ramming & Mirror Movement
Origins
Neither Ramming Movement nor Mirror Movement credits a single inventor. Both were documented and refined by the RoboWiki community as bot authors experimented with driving straight at the enemy and with copying its path instead of reacting to it.
Every technique so far in this book tries to keep the bot away from the enemy. These two point it the other way. Ramming drives straight into a collision on purpose, and Mirror Movement drives wherever the enemy just drove, trusting that the enemy's own path is a reasonable place to be.
A collision pays twice
When two bots collide, both take a fixed 0.6 damage, on classic Robocode and Tank Royale alike. Ramming turns that fixed cost into a scoring shortcut: a bot earns 2 points for every point of damage it causes by ramming, and if the ram itself finishes the enemy off, it collects a bonus of 30% of all the damage it dealt that opponent. Both numbers hold on both platforms.
A rambot drives straight at the enemy. The collision costs both bots a fixed 0.6 damage, but the rammer scores twice for it.
RoboWiki calls a bot built around this a rambot or rammer, and names GrubbmThree, LunarTwins, and NightmareTeam as strong examples in the 1v1, Twin Duel, and team formats. Nearly all of them still carry a simple gun, usually Head-On, Linear, or Circular Targeting, because closing the distance with no gun running is dangerous on its own. A rammer used as a finishing move waits until the last bullet fired at it has passed before it commits to the charge, and gives up and fires again if the ram has not landed within 300 ticks, so it does not lose the ordinary damage bonus while chasing the ramming one.
Mirror Movement copies instead of reacting
Where a rammer commits to one line, a mirror bot commits to whatever the enemy is already doing. RoboWiki describes three ways to copy it. Coordinate Mirror Movement reflects the enemy's current position across a vertical line, a horizontal line, or the battlefield center, then drives to that reflected point with a GoTo. Relative Mirror Movement copies the enemy's direction and velocity outright from the bot's own position, though it needs solid wall smoothing to keep from copying the enemy straight into a wall. Perpendicular Mirror Movement turns perpendicular to the enemy and matches its speed, orbiting it using the same bearing and velocity math the earlier movement chapters use to close or hold distance.
Coordinate Mirror Movement reflects the enemy's position through the battlefield center and drives to the reflected point.
All three variants need a decent radar lock to track the enemy accurately, and RoboWiki names PolishedRuby as the current state of the art. None of them work without that lock, since a mirror bot that loses the enemy is just guessing at where to go next.
Name the cost
A rammer's straight-line approach is exactly the predictable motion the earlier chapters on linear and circular targeting were built to punish, and RoboWiki notes the style remains largely untested against Wave Surfing or GuessFactor guns. Ramming is a strong finishing move and a weak full-time plan.
Mirror Movement's cost shows up against the opponents it should struggle with most. RoboWiki is blunt about it: the technique is "utterly useless against opponents with weak movement or anti-mirror targeting," since copying a bot that barely moves gives the mirror almost nothing to copy, and a gun built to notice the mirroring can exploit the pattern directly.
Platform notes
The 0.6 collision damage, the 2 points per point of ramming damage, and the 30% ram kill bonus all match between classic Robocode and Tank Royale. Convert bearings into one consistent angle convention before reflecting a position or matching a velocity, since classic Robocode headings are compass-style while Tank Royale headings are mathematical.
Further Reading
- Ramming Movement - RoboWiki (classic Robocode)
- Mirror Movement - RoboWiki (classic Robocode)
- Physics - Tank Royale documentation
- Scoring - Tank Royale documentation