This is a tool applying JavaScript, Node.js, and MongoDB to help you use one of the most challenging leaders in the game Puzzle & Dragons.

Puzzle & Dragons is a 7 years old mobile puzzle game. There are 30 orbs inside a 6*5 board. If you connect three or more identical orbs together, they'll form a combo.

Meanwhile, Amen is one of the most difficult character in this game. You can get insane damage if you manage to achieve it's leader skill requirement: 7 combo AND the number of remaining orbs <= 3. You can destroy almost everything in the game as long as you activate this leader skill, but it's really hard for normal players to do this.

So I came up with this tool helping people to play with Amen. I referred to some tutorials in order to find general solutions for Amen puzzles. Finally, I found that I can solve this problem quite easily. For bicolor board, I can simply print out the solutions since there are only a few possible situations. And for tricolor or multi-color board, I can use backtracking to assign the color of each combo. There are 7 combos in total, I only have to check that the neighboring combos don't have identical color. And at the end, check the number of remaining orbs is not greater than three. That's it!

function pickColor(remain, combo, rules){
    function dfs(curAns, curCombo){
        if (Math.min(...remain) < 0)
            return;
        // check the neighbors spcified in rules to be different
        for(var i=0; i<rules.length; i++){
            if(curCombo > Math.max(rules[i][0], rules[i][1])){
                if(curAns[rules[i][0]] == curAns[rules[i][1]])
                    return;
            }
        }
        // found a valid solution
        if(curCombo == combo.length){
            // use the remain drops
            for(var i=0; i<remain.length; i++){
                for(var r=remain[i]; r>0; r--)
                    curAns.push(i);
            }
            permutes.push(curAns);
            return;
        }
        // backtracking
        for(var i=0; i<remain.length; i++){
            if(remain[i] >= combo[curCombo]){
                remain[i] -= combo[curCombo];
                dfs(curAns.concat([i]), curCombo+1);
                remain[i] += combo[curCombo];
            }
        }
    }
    dfs([], 0);
}

The tool is deployed on Heroku since 7/6/2019. It got more than 4000 views within one week, and it has about 150 views per day. Feel free to use it and please contact me if you have any suggestion!

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