Six drawings on the left, six labels on the right, and a clock that keeps moving. Clear the tray to win time back.
The tray. Each round deals six pairs. Tap a drawing on the left, then the label on the right that belongs to it. Tapping in the other order works just as well.
The clock. You start with 120 seconds for five trays. A correct pair costs nothing. A wrong pair costs four seconds. Clearing a whole tray wins ten seconds back.
Points. A pair is worth 300. Three in a row lifts the multiplier, and it climbs to three times. One miss drops it back to one.
Reading the drawings. Purple means the cell held the crystal violet, so it is Gram-positive. Pink means the dye washed out, so it is Gram-negative. Red rods on a blue field are acid-fast. A dashed ring is a capsule, a clear oval inside a rod is an endospore, and a wavy line is a flagellum.
Keyboard. Tab moves between cards and Enter or Space picks one. A short reason prints under the tray after every pair.