Unit Movement System Design

The Problem: When Do I Get to the Good Part?

• Introducing a lot of systems and information the player needs to know before playing the game puts a time gated barrier between the player and the game's promised experience that can be demoralizing to overcome.

The Process: Researching & Prototyping

• We knew that we wanted to build a game with turn-based combat, so I looked at a couple different games that implemented those systems and how they made their tutorials. Afterwards, I conducted some paper playtests with the team to determine which system felt best.

The Solution: Leaning on the Familiar

• I ended up using Chess as the basis of our unit movement, due to a couple distinct advantages. First, Chess's ruleset and piece movement are quite well-known, reducing the time we needed to spend teaching the player how to play. And second, there's a lot of good documentation on how to recreate Chess movement, which I could easily adapt for our pieces' new movements.

Video Comparison: Old Unit Movement (Top) vs. New Unit Movement (Bottom)

Enemy Behavior Design

The Problem: What Are the Enemies Thinking About?

• Because the enemies in Boat Train are the primary source of challenge, we needed enemies that would act in such a way that they appeared adversarial without impeding the player's progression enough to cause frustration.

The Process: Research & Iteration

• To start, I created a move weighting algorithm that would cycle through the available pieces' moves and score them based on various criteria, then make the move with the highest score. This led to the enemy ignoring a lot of obviously good moves, which made it feel dumb. So, I looked elsewhere.

The Solution: Minimax Them

• I ended up using a modified form of the minimax algorithm that many entry-level chess bots have used to great effect. This allowed me to change the difficulty of the enemy by limiting the time the algorithm had to search for good moves, making it the perfect candidate for creating scaling challenge as the player progressed through the different levels.

Progression Design

The Problem: Why Can’t I See My Progress?

• In trying to tell a story about rising tensions, we wanted the player to have feel like they were building up to some large battle in the near future, so I needed to create a system that would evoke a sense of impending conflict and progression in the player.

The Process: Researching & Deconstructing

• To start, I looked at a couple of games that had a similar style and feeling to what we wanted, such as Shotgun King and Slay the Spire, and deconstructed how they conveyed progress to the player.

The Solution: Rallying the Troops

• I landed on a system that allowed the player to recruit a downed piece from every room to incentivize the player to engage in battle and create a dynamic akin to two armies gearing up for battle. The limited spaces the player had to place units aided in this by giving a sense of finality as they got closer to the filling all the spaces.

Video Comparison: Old recruit menu (Top) vs. New recruit menu (Bottom)