In Diatoms, you compete with your fellow players to collect and place diatom shapes into a mosaic form. You take turns placing tiles representing algae colonies. From that placement, you earn diatoms of different colors and shapes. You then strategically place these diatoms on your personal board, taking care to consider how your arrangement will be scored at the end of the game. In the base scoring, you’ll want to achieve matching colors, shape variety, and symmetry along your mosaic’s central lines. Each time you play, you may also have a “guest” judge card that brings a unique scoring criteria to the game.

Diatoms also includes a solo variant in which you collect diatom tiles as in the main game while trying to create a mosaic that fulfills specific requirements from mosaic commission prompts.