Collision Mechanics

Collisions are a critical aspect of Robocode Tank Royale. Understanding how collisions work—and how to handle them strategically—can mean the difference between victory and defeat.

Types of Collisions

There are three types of collisions in Robocode:

1. Wall collisions - When your bot hits an arena wall
2. Bot-to-bot collisions - When your bot collides with another bot
3. Bullet collisions - When bullets hit bots or walls

Wall Collisions

When a bot collides with a wall, several things happen:

• The bot is immediately stopped (speed becomes 0)
• The bot takes damage proportional to its impact speed
• The bot may bounce slightly off the wall

Wall Collision Damage

The damage formula for wall collisions is:

$\text{damage} = \max(|velocity| - 1, 0)$

This means:

• Moving at speeds ≤ 1 unit/turn = no damage
• Moving at 8 units/turn = 7 damage points
• The faster you hit the wall, the more it hurts

Avoiding Wall Collisions

Basic wall avoidance strategies include:

• Distance checking: Monitor your distance to walls using arena boundaries
• Wall smoothing: Adjust heading to parallel the wall when approaching
• Predictive braking: Start decelerating before reaching the wall

For advanced wall avoidance techniques including wall smoothing algorithms, see Wall Avoidance & Wall Smoothing in The Book of Robocode.

Bot-to-Bot Collisions

When two bots collide:

• Both bots take 0.6 damage per turn while in contact
• Both bots are typically stopped
• Exception: If a bot is moving away from the collision point, it may continue moving

Collision Physics

Bot-to-bot collision behavior:

• Bots cannot pass through each other
• If bots are perpendicular or approaching, both stop
• If one bot is retreating from the contact point, it may continue
• Collision damage accumulates each turn bots remain in contact

Strategic Considerations

Ramming can be an offensive tactic:

• Useful when you have more energy than your opponent
• Each collision inflicts 0.6 damage but costs you 0.6 energy too
• See Physics - Ramming for ramming damage calculations

Avoiding collisions is often preferable:

• Maintain minimum safe distance from opponents
• Use predictive movement to avoid being trapped
• Consider collision zones in your movement algorithms

For advanced collision handling strategies, explore movement techniques in The Book of Robocode.

Bullet Collisions

Bullet-Bot Collisions

When a bullet hits a bot:

• The target bot takes damage based on bullet firepower (see Physics - Bullet damage)
• The shooter gains energy (3 × firepower)
• The bullet is removed from the battlefield

Bullet-Bullet Collisions

Bullets can collide with each other in mid-flight:

• Both bullets are destroyed
• No damage is dealt to any bot
• This is relatively rare but can happen in crowded battles

Bullet-Wall Collisions

When bullets hit walls:

• The bullet is destroyed
• No damage is dealt
• No energy is transferred

Working with Collision Events

The Bot API provides events for handling collisions:

Wall collisions:

onHitWall(HitWallEvent event)

Bot collisions:

onHitBot(HitBotEvent event)
onScannedBot(ScannedBotEvent event) // To avoid collisions

Bullet hits:

onBulletHit(BulletHitEvent event)
onHitByBullet(HitByBulletEvent event)

See the Bot API documentation for complete event details.

Collision Strategy Summary

Situation	Recommended Action
Near wall	Slow down, turn parallel, or use wall smoothing
Enemy nearby	Maintain safe distance or ram if you have energy advantage
Low energy	Avoid all collisions—every hit matters
High traffic area	Use predictive movement to navigate clear paths

Further Reading

• Physics - Core physics equations and movement constraints
• Movement Fundamentals - Basic movement techniques
• Wall Avoidance & Wall Smoothing - Advanced wall handling
• Anti-Gravity Movement - Collision avoidance through repulsion fields