Yea its true that its completely randomized, I tried to beat my score again but didn't manage to do it.
Its true about the game jam, the time constraints doesn't lets you add or fix some things and that is the challenge of it.
I don't know how one could tune the luck chance since I have no way of knowing how.... Hmmm maybe have a big number? Like instead of choosing from 1 to 6 you choose from 1 to 12. That way by checking the next 2 customers drinks you assign the values that you want more chance to add.
Example: Customer #1 wants 1 + 4
and Customer #2 wants 2.
You could assign to the list what numbers you want to output 1, 2 and 4.
Like for (1) gets assigned 1, 7, 8.
(2) 2, 9, 10.
(4) 4, 11, 12.
Before assigning its value, you check if the number is already taken and check the next one to take.
This way each 1, 2 and 4 have a 25% chance of being selected.
And the other ones: 3, 5 and 6 have a 8% of being selected.
You could experiment on that, like it could be used for a future game if you are going to use random selection.
Maybe instead of choosing a random location for each number, it could be like this:
Like for each future number you assign it in an ascending order, also having other checks so the last numbers still have a number assigned.
It doesn't has to be 12, it could be more.
Next customer values: 5+4, 2+1
(1) = 1,2,3;
(2) = 4, 5, 6;
(4) = 7,8;
(5) = 9,10;
(3) = 11;
(6) = 12;
Something on those lines, there has to be some videos on YouTube explaining about it.
I hope that helped a bit.