Haddex

A falling-hexagon arithmetic game: wherever three hexagons meet at a corner and one number is the sum of the other two, all three vanish.

Category: Game
Format: Single-player, in the browser
Language: English
Author: Olga Malyuk

Haddex start screen: the rule “Pieces fall. Where three hexes meet at a corner, if one is the sum of the other two, all three vanish and everything above falls”, with the example 4 + 5 = 9 and a Start button. — Keyboard: arrows to move and rotate, Space to drop, C to hold, P to pause. Click the board first if the keys don’t respond. On a phone the game opens on its own page, with touch buttons under the board. There is no sound.

§1How it plays

Pieces of one to three hexagons fall into a well of hexagons. Wherever three hexagons meet at a corner and one number is the sum of the other two, in any order, all three vanish. Everything above falls straight down, so one sum can set off a chain of others.

The rules never change as you level up; the numbers grow instead. Every 15 hexagons cleared is a new level: 1 to 9 at first, then up to 12, 15 and finally 20. Chains, and several corners at once, score more.

§2Tuning the rules

Haddex grew out of ADJOIN, a two-player hexagon placement game with the same corner rule, built together with a simulation lab. Rule choices for Haddex were tested with bots that either drop pieces blindly or look for sums. Because a number above 9 can only ever be the result of a sum, large numbers are made rarer and a piece carries at most one. Without that, a bot weighing every option still stacked out in 6 of 30 simulated games; with it, in none.