24ga.me: play the 24 card game without a deck
At IMPA, one of the most popular games 1 to play between classes is "24". Here’s how it works:
Four cards are drawn from a deck.
Using each card exactly once and the four basic operations (+, −, ×, ÷), players race to combine them to make 24.
As soon as someone finds a solution, they clap twice (clapping once means nothing, it acts as a safeguard if you mistakenly think you’ve solved it).
The last player to clap must challenge another to present their answer. If the challenged player fails, they collect the cards; otherwise, the challenger takes them.
The goal is to end up with the fewest cards (though we rarely keep score).
If everyone agrees, one card can be swapped for a fresh one, but the replaced card still counts against whoever loses the round.
The game is fast, easy to learn, and people can join at anytime.
One day in the tea room, we couldn't find a deck to play. I Googled for a site that would draw 4 random cards but couldn't find a good one, so I quickly coded one for us. Later, at home, I came up with a cool domain name, polished the site, and eventually launched 24ga.me. The site also lets you check whether a solution for the current round exists or not.