Wall Collisions

The battlefield has hard boundaries called walls. When your bot collides with a wall, it takes damage and stops moving. Understanding walls and learning to avoid them is one of the first skills every competitive bot must master.

What Are Walls?

Walls are the invisible barriers at the edges of the battlefield. They form a rectangular boundary:

• The bottom wall is at y = 0.
• The left wall is at x = 0.
• The top wall is at y = battlefieldHeight.
• The right wall is at x = battlefieldWidth.

Your bot cannot move beyond these edges. If you try, your bot will collide, stop, and take damage.

Battlefield Dimensions

Battlefields vary in size depending on the battle type and format. The allowed size range and standard configurations are:

Size Range

• Minimum size: 400 × 400 units
• Maximum size: 5000 × 5000 units

Standard Battle Sizes

• 1v1 (Standard): 800 × 600 units
• Melee (Free-for-all): 1000 × 1000 units

Larger battlefields give bots more space to maneuver and evade, while smaller battlefields force closer combat. The dimensions affect movement strategy significantly—on a 400 × 400 battlefield, escape routes are limited, while a 5000 × 5000 battlefield allows for extended long-range engagements.

Damage from Wall Collisions

When your bot hits a wall, you lose energy based on your velocity at impact:

• Classic Robocode: You take damage equal to abs(velocity) * 0.5 - 1 energy per hit.
• Robocode Tank Royale: Similar damage rules apply, scaled to velocity on impact.

For example, hitting a wall at full speed (8 units/turn) in classic Robocode costs you (8 * 0.5) - 1 = 3 energy. Multiple collisions quickly add up, and can disable or destroy your bot.

Tip: Collisions also bring your bot to a complete stop, wasting precious movement time and making you an easy target.

Why Wall Avoidance Matters

Avoiding walls is critical for several reasons:

1. Survival: Every collision drains your energy. Repeated hits can cost you the match.
2. Mobility: Being stuck on a wall means you can't dodge enemy bullets effectively.
3. Predictability: Bots that hug walls are easy to target — experienced opponents know where you'll be.

Elite bots rarely touch walls except in very specific tactical situations. Learning to maintain safe distances from boundaries is a foundational skill.

Simple Wall Avoidance

The most basic wall avoidance strategy is to check your distance from each wall and reverse or turn before you get too close:

if distance to nearest wall < safeDistance:
    reverse direction
    or turn away from wall

For example, if your bot is moving forward and nears the top wall, you can:

• Call setBack(distance) to reverse.
• Call setTurnRight(angle) or setTurnLeft(angle) to steer away.

A common safe distance is around 100–150 units from the wall, giving you plenty of room to maneuver and dodge.

Advanced Considerations

As you improve, you'll refine your wall avoidance:

• Predictive movement: Calculate exactly when you'll reach the wall based on your current velocity and deceleration rate, and plan your turn in advance.
• Wall smoothing: Move parallel to walls at a safe distance, rather than bouncing away abruptly. This keeps your movement fluid and less predictable.
• Tactical positioning: Sometimes staying near (but not touching) a wall can limit the angles an enemy can attack you from — but only if you're confident you can dodge effectively.

These techniques are explored in depth in the Movement & Evasion section of this book.

Platform Notes

Wall collision damage formulas are slightly different between classic Robocode and Tank Royale, but the core principle is the same on both platforms:

• Walls are fixed rectangular boundaries.
• Hitting them costs energy and stops movement.
• Avoidance is essential for competitive play.

Further Reading & References

• RoboWiki - Wall Avoidance
• IBM DeveloperWorks - Fighting with Algorithms
• Robocode Tank Royale - Physics
• Movement Constraints & Bot Physics — for velocity and deceleration formulas
• Coordinate Systems & Angles — for battlefield dimensions and position tracking

Linking Forward

Once you understand wall collisions, you're ready to explore more sophisticated movement strategies. See the Movement & Evasion section for advanced wall smoothing, orbital movement, and wave surfing techniques that help you stay mobile and unpredictable.