Some strategies are triggered automatically when the player enters a specific region. To prevent this from happening, if a new primary target is only marginally better than the current target, CastlevaniaBot may choose to stay on its current course. If it failed to do so, it could get stuck in an infinite loop, switching back and forth between 2 targets with equal or nearly-equal ranks. After whipping the bat, it can resume handling the candles.ĬastlevaniaBot considers the current target and strategy before deciding to switch. Depending on how close it is to the bat, CastlevaniaBot may respond by switching from the candles strategy to the bat strategy. For example, CastlevaniaBot might be about to strike some candles when a bat flies into frame. The top rank is the primary target and when the primary target changes, it switches strategies. The decision process uses a fitness function to rank all the onscreen game objects. For instance, there is a strategy for dealing with skeletons, another for fishmen, another for whipping candles, another for collecting hearts, and so on.ĬastlevaniaBot constantly monitors the game state and it switches between the available strategies as it deems necessary. Most of them are designed to handle a particular game object type. Creating it involved articulating in elaborate detail the physics that govern Simon Belmont’s 8‑bit world and all the tactics required to be an expert vampire killer.ĬastlevaniaBot has access to a catalog of strategies for handling a wide range of situations.

The result is a system that simulates the same decision-making process that I perform when I have a controller in hand. And the challenge was to capture my knowledge into a computer program. If anything, its development might be called “machine teaching”. This project does not involve machine learning. In this article, I describe how I created a bot that’s able to beat Castlevania and how you can do the same for other NES titles. Or you can intermittently start and stop it at any point in the middle of a game and let it complete a section. If you launch it during the title screen, it will play through the entire game from start to finish. CastlevaniaBot is a plugin for the Nintaco NES emulator that plays Castlevania.

Castlevania dialog maker