De-Block is a puzzle game that can be explained as a 4-way Tetris-like game. The player controls a block in the center of the screen which can move and rotate freely. Larger blocks move inward from each side of the screen and attach to the center block, then change color depending on their distance from the center. If the player completes a colored ring, that layer and all the blocks inside of it are cleared, and all the ones outside are moved inward.
The gameplay is centered around clearing lines by creating sets of matching colors. The game gets increasingly difficult as more blocks appear on screen, making it harder to plan ahead and make strategic moves. The player must think carefully about which blocks to move and rotate in order to clear as many lines as possible before the new block overlaps with their structure.