Fomo3D automation with a single entry point: letsGo deploys a throwaway player funded with a tenth of an ether that buys, withdraws and destroys itself in one transaction.
Historical Significance
Fomo3D paid whoever acted last and most, and the round became a contest between contracts rather than people. This one is the pattern reduced to a single call: anyone can invoke letsGo, the affiliate and team are fixed so the operator collects the referral regardless of who pays the gas, and the child leaves nothing behind. Creating and destroying a contract inside one transaction also earned a gas refund at the time, which made the loop cheaper than it looks.
Key Facts
Description
The parent has one function. letsGo deploys a child with exactly 0.1 ether and the caller's address, and does nothing else; there is no owner, no storage and no way to configure it.
The child does all the work in its constructor and never has a runtime. It buys keys with its incoming value naming a fixed affiliate and team, immediately calls withdraw to pull back whatever the game credited, then loops: while its balance is still above 0.13 ether and more than two hundred thousand gas remains, it buys and withdraws again. The loop counter is halved each pass rather than being recomputed from the balance, so it is a bounded retry count rather than a real balance check. When it stops, the child selfdestructs to the address that called letsGo.
Every buy in the loop sends msg.value, the amount the constructor received, not the current balance. Combined with the halving counter this makes the number of passes a function of how much was sent, not of how much the game paid out.
Source Verified
Byzantium Era
First Metropolis hard fork. Added zk-SNARK precompiles, REVERT opcode, and staticcall.
Bytecode Overview
Verified Source Available
This contract has verified source code.
View Verification ProofShow source code (Solidity)
// Submitted by EthereumHistory (ethereumhistory.com)
pragma solidity ^0.4.24;
contract Game {
function buyXaddr(address _affCode, uint256 _team) public payable;
function withdraw() public;
}
contract Player {
constructor(address _owner) public payable {
Game(0xDd9fd6b6F8f7ea932997992bbE67EabB3e316f3C).buyXaddr.value(msg.value)(0xeB54F65775e6A2A42e243823D86486A64Fd1f0d6, 2);
Game(0xDd9fd6b6F8f7ea932997992bbE67EabB3e316f3C).withdraw();
uint256 bal = address(this).balance;
while (bal >= 0.13 ether && gasleft() > 200000) {
Game(0xDd9fd6b6F8f7ea932997992bbE67EabB3e316f3C).buyXaddr.value(msg.value)(0xeB54F65775e6A2A42e243823D86486A64Fd1f0d6, 2);
Game(0xDd9fd6b6F8f7ea932997992bbE67EabB3e316f3C).withdraw();
bal = bal / 2;
}
selfdestruct(_owner);
}
}
contract Bot {
function letsGo() public payable {
(new Player).value(0.1 ether)(msg.sender);
}
}