Writing a Simple Bot

In this guide, we will learn how to write a simple bot that will play in bot royale.

See also: A primer on rules and mechanics and Using the GUI app

Setting Up

Install Bot Royale and create your python script (e.g. main.py). Let's begin with this simple boilerplate:

# main.py
import botroyale as br


class MyBot(br.BaseBot):
    NAME = 'testing new bot'

    def poll_action(self, state):
        return br.Idle()


br.register_bot(MyBot)
br.run_gui()

When we run this script it creates a bot that always idles, registers it, and then runs the app. In the main menu, we can select our new bot ("testing new bot" is their name) and start a new battle.

Actions

Our new bot isn't doing anything - it is using the Idle action every time. The idle action ends our turn. Let's make our bot use the Move action.

The Move action takes a target parameter (of type Hexagon). The target is where we want to move to. We also know that Move only allows moving 1 distance away. So we must find our target hex that is 1 distance away from us. This is done very easily with Hexagon.neighbors.

Let's adjust the code in poll_action:

# main.py
import random
import botroyale as br


class MyBot(br.BaseBot):
    NAME = 'testing new bot'

    def poll_action(self, state):
        """Called by the battle as long as it is our turn. Returns an Action."""
        my_pos = state.positions[self.id]  # Find our position
        move_targets = my_pos.neighbors  # Find our possible targets
        target = random.choice(move_targets)  # Choose a neighbor at random
        return br.Move(target)


br.register_bot(MyBot)
br.run_gui()

Now our bot will move to a random direction every time. However it is also showing some glaring issues: it may kill itself by moving outside the ring of death or onto a pit, it may make an illegal action by bumping into other units or walls, and it always ends it's turn with an illegal action (because of missing AP).

Note: If for any reason the code causes a crash, the bot will be killed instead (showing a death icon with a red background). If this happens, you know the code has an error that is logged; see console output. Illegal actions have no penalty except that they end the turn (as if Idle was used).

Inspecting the state object

Let's fix some of these issues. First we will avoid suicide by checking the ring of death and pits with a new check_safe function that we will write. Then we will avoid illegal moves by using the State.check_legal_action() method. We will use center_distance() to check our distance from the center of the map.

# main.py
import random
import botroyale as br
from botroyale.api.bots import center_distance


class MyBot(br.BaseBot):
    NAME = 'testing new bot'

    def poll_action(self, state):
        """Called by the battle as long as it is our turn. Returns an Action."""
        my_pos = state.positions[self.id]  # Find our position
        move_targets = my_pos.neighbors  # Find our possible targets
        # Filter out targets that are not safe
        safe_targets = [hex for hex in move_targets if self.check_safe(state, hex)]
        random.shuffle(safe_targets)  # Randomizing for demo purposes
        # Look for a legal action with our safe targets
        while safe_targets:
            next_target = safe_targets.pop(0)
            action = br.Move(next_target)
            if state.check_legal_action(action=action):
                return action
        # No move targets were safe and legal, let's finish our turn
        return br.Idle()

    def check_safe(self, state, hex):
        """Check if it is safe to move to a tile."""
        if center_distance(hex) >= state.death_radius - 1:
            # This hex is outside or threatened by the ring of death
            return False
        if hex in state.pits:
            # This hex has a pit
            return False
        return True


br.register_bot(MyBot)
br.run_gui()

Now when we run the game, our bot doesn't suicide and does legal actions only. I see you're getting the hang of this, so I'll let you continue from here :)

Final notes

In this guide we learned how to write a simple bot that can play and is aware of the game state. It is highly recommended to study the bot developer API.