Gun Heat & Cooling

Firing is never “free” in Robocode. Each shot heats up the gun, and a hot gun can’t fire again until it cools back down.

That means good bots don’t just aim well — they time their shots so the gun is ready when it matters.

Why gun heat matters

Gun heat is a built-in reload mechanic.

• If the gun is too hot, fire() / setFire() won’t produce a bullet.
• Heat depends on bullet power: stronger bullets create more heat.
• Cooling is gradual and happens at every turn.

This creates a simple trade-off:

• High power: more damage per hit, but longer downtime between shots.
• Low power: faster rate of fire, but weaker bullets.

A classic “good moment” to have zero gun heat is when an enemy is in trouble — cornered, stuck on a wall, or disabled (not moving). Being ready then is often worth more than shooting "as soon as possible."

Initial gun heat

Bots start each round with their gun already hot:

• Initial gun heat: 3.0 (both Classic Robocode and Tank Royale)
• Default cooling rate: 0.1 heat per turn

This means bots cannot fire immediately at round start. With default settings:

$T_{\text{first shot}} = \frac{3.0}{0.1} = 30 \text{ turns}$

The first shot is possible on turn 30. This gives bots time to scan, position, and aim before the first shots are exchanged.

Opening moves

Use the first 30 turns wisely! Scan all enemies, establish radar lock, move to a favorable position, and pre-aim your gun. When turn 30 arrives, you should be ready to fire immediately.

The gun heat formula

In classic Robocode (and similarly in Tank Royale), firing adds heat based on bullet power.

Let:

$p$ = bullet power (typically 0.1 to 3.0)
$H$ = current gun heat

Then the shot increases heat by:

$\Delta H = 1 + \frac{p}{5}$

So after firing:

$H \leftarrow H + \left(1 + \frac{p}{5}\right)$

Quick intuition:

• Power 1.0 adds: $1 + \frac{1}{5} = 1.2$ heat
• Power 3.0 adds: $1 + \frac{3}{5} = 1.6$ heat

Cooling rate (and how long you must wait)

Each turn, gun heat is reduced by the gun cooling rate.

Let:

$c$ = gun cooling rate (default is 0.1 heat per turn, but game rules can change it)

Cooling per turn:

$H \leftarrow \max(0, H - c)$

If the gun heat right after firing is $H_{\text{after}}$, then the number of turns until you can fire again is roughly:

$T_{\text{cool}} = \left\lceil \frac{H_{\text{after}}}{c} \right\rceil$

Example with default cooling (c = 0.1):

• Fire with power $p=1$: $\Delta H = 1.2$ → about $\lceil 1.2 / 0.1 \rceil = 12$ turns
• Fire with power $p=3$: $\Delta H = 1.6$ → about $\lceil 1.6 / 0.1 \rceil = 16$ turns

That’s a big difference in how often the bot can shoot.

Minimal shooting logic: always check heat

A common beginner bug is calling fire() every turn and assuming it will always shoot.

A safer pattern is:

# Decide whether it is worth firing this turn
power = chooseFirePower(enemyDistance, enemyEnergy, hitChance)

# Only shoot if the gun is ready
if gunHeat == 0 and power > 0:
    fire(power)

Two practical upgrades:

• If gunHeat is close to zero, it can be worth delaying aim changes so the gun is perfectly aligned when heat hits zero.
• If the bot relies on radar locks, it can adjust scanning behavior based on expected fire time.

Platform notes (Classic vs Tank Royale)

The concept is the same on both platforms: shots add heat, and heat must cool to zero before the next shot.

Differences to watch for:

• Where to read the values: APIs differ, but both provide access to current gun heat and the cooling rate/rules.
• Configurable rules: the default cooling rate is commonly (0.1), but battles can be configured with different rules. If a bot hard-codes (0.1), it may perform badly under custom settings.

Tips and common mistakes

• Don’t waste “ready turns”: if the gun is at zero heat, but the bot doesn’t have a target solution ready, that’s a missed opportunity.
• Avoid panic-power: firing max power at long distance usually means low hit chance and long cooldown.
• Separate “aiming” and “firing” decisions: aim can be updated at every turn, but firing should be gated by heat.
• Remember the goal: the best shot is often the one fired at the best moment, not the earliest moment.

Gun heat after firing and then cooling linearly each turn (c = 0.1). Higher bullet power starts hotter and takes longer to cool: p=1 (ΔH=1.2) reaches 0 after ~12 turns, while p=3 (ΔH=1.6) reaches 0 after ~16 turns.

Legend:

• Green: p=1.0 (ΔH=1.2)
• Blue: p=3.0 (ΔH=1.6)

Further Reading

• Gun Heat — RoboWiki (classic Robocode)
• Robocode Tank Royale - Physics — Tank Royale documentation