TLDR

I used Cursor to create a Ruby implmentation of the War card game. You can check it out at https://github.com/toddmuchmore/ruby-war/.

The game that never ends

My kids and I recently have been playing the card game War. The game never ends. I thought it would be a fun weekend project to write a Ruby program to simulate the card the game so that we could see how long the game actually takes to complete.

I sat down and started to think about how I would approach this and then had the idea that this seems like a perfect use case to try out Cursor and see what it could be capable of.

First iteration

I started off by using the Cursor agent and prompting it with:

I’d like to create a Ruby command line application for the card game “war”.

When run, the user should be prompted for player a’s name, player b’s and the number of games to play.

I was planning on writing more information but accidentally hit return instead of shift-return 🙃, but I figured I’d let it go and would add additional information as we went.

I was surprised to learn that it knew what the game was and it created a basic implementation of it. It didn’t get everything right though. It just kept track of the number of rounds won for each game and then used that determine the overwall winner. It also had no concept of a “war” when players played the same card.

Second iteration

I figured it might be better to just start from scratch. I created a new file called “rules.md” and wrote down all of the rules of the game. I then prompted it to:

I’d like to start over from scratch. Can you look at the rules I have laid out in @rules.md?

I’d still like to perform the same basic concept of the game, collecting the names of the players, the number of games to play, etc. But I want you to use the rules defined in rules.md instead.

This time it worked perfectly. I did exactly what I wanted. It let me know about changes it made and why it made them.

It was pretty cool to see that the first run through. It showed that it took 218 rounds for the game to end.

Third iteration

I wanted to have the ability to simulate a large number of games. So I prompted it to

I’d now like to add in the ability to ask the user how many games they would like to play. It should then play that number of games and keep track of the number of wins each player had. I’d also like to output the average number of rounds that the all of games took.

This one took a bit of back and forth. The update it made, it would ask for the players names each time. I told it about that and it made the correct updates to only ask for the players names at the begining of the simulation.

Conclusion

This was a lot of fun. The final output of the program did exactly what I wanted and it was neat to show my kids the program and the results.

I just ran 1000 games and here are the results:

Final Results
============
Games played: 1000
Player A: 518 wins
Player B: 482 wins
Average rounds per game: 246.14

That’s a lot of rounds.

If you want to take a look at the code it generated, I put it up over at: https://github.com/toddmuchmore/ruby-war/.