Tarot

This is an implementation of Kingdominion that I wrote so I could write an AI to play against.

Using it

Fire up a console

bin/console

Then create an initial gamestate with

state = Tarot::State.new

You can check out the available moves with

state.available_moves

Or try out one of the moves with

state2 = state.play_move(move: game.available_moves.sample)

Each command you run should duplicate the state, muck around with the new one, and then freeze it, so you can also still keep doing this and try different moves

state3 = state.play_move(move: game.available_moves.sample)
state4 = state.play_move(move: game.available_moves.sample)
state5 = state.play_move(move: game.available_moves.sample) 

Notes

State Phases

• :init_claim
• :init_commit Repeat until all old_claims are taken
• :claim
• :place
• :commit

What's the deal with rand?

It's important to explicitly define the random seed, so that the same gamelist can be played through repeatedly without having to reshuffle the tiles. However, the computer AI can't be allowed ot have knowledge of the tiles to be drawn, because the computer can't cheat.

One method of tackling this would be to develop a heuristic where the computer looks at the distribution of tiles left; sort of like card counting in blackjack... however this really bakes in the strategy that the AI will use and makes it relatively predictable. The advantage here, however, is that it would allow us to go relatively deep in the game-state-space.

Another strategy would a stochastic monte carlo search the same moves a handful of times. The idea here is that the move (especially a later-game move) might be good 50% of the time, so let's go for it, while a bad move might only be good 10% of the time. Usually it's going to pick a decent move.

Another benefit of going about it this way is the computer will never play perfectly. Sometimes it will make a wildcard play that appears to be bad, even though in its imagined trials, it happened to luck out.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

License

The gem is available as open source under the terms of the MIT License.

Thanks

• https://github.com/PragTob/rubykon - for his ruby implementation of MCTS, of which this was derived.

• https://github.com/dbravender/tilerealm - for his python implementation of the game. It turns out enumerating possible places to drop a tile is hard.