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Editorial Team
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Asked: 2026-06-18T10:03:38+00:00

What’s a decent level-generation algorithm for a game similar to Unblock Me? My first

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What’s a decent level-generation algorithm for a game similar to Unblock Me?

My first attempt was to start with a solved level and work backwards. I started with the red horizontal rectangle next to the exit on the right side of the board. Initially the board has zero other pieces. So I tried to add pieces pseudo-randomly up to the desired piece count (say seven). Levels limited to only horizontal or only vertical pieces are not very interesting so I alternated between horizontal and vertical pieces while adding. Finally I tried to scramble the pieces by moving them randomly. After working through a few examples it became obvious that this method often generates uninteresting levels. Also the minimum move count is unknown.

The next attempt approaches the problem in a different way. Levels are generated randomly. Then a search algorithm finds the minimum number of moves to solve the puzzle (if it’s possible). While I haven’t implemented this yet I think it will create some interesting levels. Since the board is relatively small (10×10 upper bound) I think the run time will be acceptable for generating levels that are bundled with the app. Also the minimum move count is known which is important for scoring.

I doubt the first approach works as is. However a variation that I haven’t considered could work. My only reservation with the second approach is the potential code complexity. I think it will be a BFS with a memo table and a BoardState object. I’d like to hear some alternatives before diving into the second approach.

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1 Answer

  1. Editorial Team

    I would do like this:

    • Generate a random state of the game where the red rectangle is next to the exit
    • Calculate the full state space for the board starting from that state
    • Choose one of the states in the state space that is furthest away from a solved state as the actual problem. I would use as distance measure the number of moves of distinct pieces, i.e. count multiple moves of the same piece in a row as 1
    • If the generated state space is too small, remove pieces and redo
    • If the generated state space is large but distance from any state to solution is small, add pieces and redo
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