Eth17, A brand new Ethereum smart contract based FOMO (Fear Of Missing Out) game launches on 19th November.

The game concept is extremely simple. It is effectively a game of “higher or lower” on the Ethereum blockchain. The smart contract behind the game requests a random number from an Ethereum oracle (in this case Oraclize) which is then privately encrypted and stored in the smart contract.

The number generated is always between 1 and 1,000,000 and players have a maximum of 17 guesses per game to guess the number. If you guess the correct number, you will all the Eth stored in the smart contract!

Now with a number range so huge, it would be practically impossible to guess the number, so the game provides clues after each guess. It will tell you if the next guess should be higher or lower than the previous guess. So for example if your first guess is 500,000, it might tell you that you need to go lower, in which case the number range would now be between 1 and 500,000.

If you then guessed 250,000 it may tell you that you would need to go higher on the next guess, therefore your new guessing range would be between 250,000 and 500,000.

Fortunately the game keeps tabs on all guesses, and you can immediately see what the current range is. It even assists you by providing a suggested number in the “guess” field, which equates to exactly half-way between the current number range (so if the current range was between 200,000 and 600,000 it would suggest 400,000 as a new guess)

So why bother playing the game if the range is so high? Well the FOMO twist is that there is a 10-minute countdown timer. If you make a guess and you are wrong, the countdown timer starts ticking down, and if the timer reaches zero without anyone else making a guess, then you will win all the Eth in the contract anyway. If someone else does happen to make a guess within the 10-minute period, then the countdown timer resets back to 10-minutes, and they become the last player and are therefore in line to win all the Eth in the contract if the timer reaches zero.

The first guess for each game is free (apart from a tiny gas cost to actually “write” your guess onto the smart contract) so there is an obvious incentive to start each game. Also the early guesses are extremely cheap (guess #2 is 0.0025 Eth). The cost of each guess increases slightly, rising all the way up to 0.1 Eth for the 17th and final guess, although you are actually refunded your Eth on the 17th guess if you get it wrong.

If nobody guesses correctly after 17 guesses, the privately stored number is revealed, and a new game is generated with a new random number. The Eth stored into the contract rolls over onto the next game, and will increase by 0.2 Eth for every new game launched.

The team behind Eth17 will be adding all of the smart contract code onto Github 24hrs prior to main-net launch and will be verifying the smart contract on Etherscan so that solidity programming experts can publicly confirm exactly what the contract is doing in the background.

The game is currently running on the Kovan test network in beta, and can be seen at www.eth17.com