Update the smart contract to use hashes to hide the choice of players.
The solution is shown below so only look if you have had a go at solving it yourself and make sure to watch the video first.
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pragma solidity 0.6.0;
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contract Game {
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bytes32 ROCK = keccak256(abi.encodePacked("ROCK"));
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bytes32 PAPER = keccak256(abi.encodePacked("PAPER"));
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bytes32 SCISSORS = keccak256(abi.encodePacked("SCISSORS"));
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mapping(address => bytes32) public choices;
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function play(bytes32 choice) external {
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require(choice == ROCK || choice == PAPER || choice == SCISSORS); // checks that move is valid
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require(choices[msg.sender] == bytes32(0)); // make sure player hasnt played before
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choices[msg.sender] = choice;
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}
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function evaluate(address alice, address bob)
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external18
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returns (address)
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{21
if (choices[alice] == choices[bob]) {
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return address(0);
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}
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if (choices[alice] == ROCK && choices[bob] == PAPER) {
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return bob;
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} else if (choices[bob] == ROCK && choices[alice] == PAPER) {
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return alice;
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} else if (choices[alice] == SCISSORS && choices[bob] == PAPER) {
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return alice;
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} else if (choices[bob] == SCISSORS && choices[alice] == PAPER) {
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return bob;
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} else if (choices[alice] == ROCK && choices[bob] == SCISSORS) {
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return alice;
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} else if (choices[bob] == ROCK && choices[alice] == SCISSORS) {
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return bob;
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}
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}
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}
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