Simple coin flip game for Waves blockchain tokens needed

I need a simple coin flip game for the blockchain tokens on the Waves cryptocurrency platform. Head wins, tail loses. How the off blockchain script should work: 1. I set the game up, so I chose which ones from all the Waves tokens available I want to fill the bankroll with and what the maximum bet is. 2. User comes to site, chooses in which token he wants to play the coin flip and deposits to play. User has to pay the transfer out fee to the blockchain. That is basically it. Script must be hacking proof. Payment after script delivery with setup instructions, no settlement outside Freelancer, as I got scammed once and lost a lot of money. If project is successful, follow up work will be needed.