My recent question was answered by "Stiv", and I green-checked it. Then I accidentally undid it twice. Is it actually possible to undo green checks, just like votes?

You are playing a series of 100 games of rock-paper-scissors^ against your friend. From your past games, you know that he will choose exactly 40 rocks, 35 papers and 25 scissors in some random order. What should be your strategy to maximize the number of wins over the 100 games? ^ Rock beats scis...

This puzzle is part of the Monthly Topic Challenge #7: Board games. Inspired by the incident, I created a variant of Mastermind, although it wasn't actually intended for colorblind people. The main difference is that you don't know what the small pegs exactly mean in the first place. You just kn...

I am found in many lands, from the mountains to the sands. I bring you joy and sometimes pain, and can make you play again. What am I?

At 5:15AM yesterday a cryptic radio transmission was received from a top-secret research facility which lasted about 6 minutes. After that we were unable to reestablish contact for nearly an hour. The message was as follows: 72 68 116 15 108 99 103 59 80 99 57 46 84 13 81 1 8 31 68 41 112 118 28...

I am not alive, but I grow; I don't have lungs, but I need air; I don't have a mouth, but I need water to live. What am I?

This puzzle is part of the Monthly Topic Challenge #7: Board games. If we're using rooks, then this would be equivalent to a classic "fifteen puzzle" though on a larger grid. This time we'll use knights instead of rooks. Place sixty-three knights, each in a different color, on the 8x8 chessboard...