Thank you very much for the statement and the link. I will see what I can change to make it more "provably".
Until then please just believe me (and the code) that my intention is not to trick anybody.
That's the problem. It's not about you personally. It's about "the unknown" and you just happen to be part of it. Just like I was. In this bitcoin world, provable fairness is now a requirement, or no one is going to play the games. (or most people won't).
Get your random numbers from somewhere that publishes it and maintains a record, or generate your own and hash them with SHA-256
An example would be:
secret = RgIzrY9dGD8NBcxb1cDzeywgl1YJNj7jnccdZTvpkVlSws97ep6efb9IW6p9IITC
sha256 result = ec1399de44e7b3cb62773f28de0b631a5fc7b7bd22c16e08537ba97d4d118899
Where you can publish the hash before the game. And then use the secret to determine the fastest coin runner. Then after the game, you also publish the secret. Then people can verify that you used that same secret to compute the winner, and also that you didn't change the secret during the course of the game.
But you need another part (from an external source), something that you can't control or know. Otherwise you can play your own game and let your own coin run the fastest.
You have to be able to prove that you can't do that.
Once you satisfy those two minimum requirements, people may then play your game. The question of if they will actually play it is another matter, as I've seen some perfectly good websites have no players at all despite being provably fair.
The other part that can't be proven with math or code is trust, and that's going to be much harder to "prove". You or your website have to earn it, slowly, over time.
You can make it quicker by posting your complete dox, but I doubt you'll do that.