Labyrinth.sol

// this labyrinth contract as a public utility can be used as an "entropy crawler", 
// using the state itself as a source of entropy (generated entirely from human social coordination 
// that is highly random. )

contract Labyrinth {

  uint entropy;
  
  function getRandomNumber() public returns (uint) {
    entropy ^= uint(blockhash(entropy % block.number));
    return entropy;
  }

}