Incorrect Use of Global Variables

handler.js

let config = {
    minimumScore: 50,
};

exports.handler = async (event) => {
    
    const { score, mode } = event;
    
    let minimumScore = config.minimumScore
    
    if ( mode === 'hard') {
        minimumScore = 25;
    }
    
    if (score < minimumScore ){
        return `You need to score higher to get onto the ${mode} leaderboard. ${score}/${minimumScore}`;
    }
    
    return `Congratuations! You made it onto the ${mode} leaderboard. ${score}/${minimumScore}`;
};