PotoPoto or Poto Poto (ポトポト) is a 1994 puzzle game by Sega released exclusively in Japan exclusively on System C2 hardware.
The well is a comb of hexagons and the pieces (poto) are hexagonal. A new piece comes each time the character above the well hovers over one of the three spaces that is lower than the others. You have a limited time to move the piece to where you want it to be before it falls. Get four or more of the same color touching to remove the pieces from the well. If removing a piece results in the pieces immediately above and below to be left with a gap between them, the pieces below are also removed. Occasionally a bomb will be thrown at you; move it around and hit the button to drop it, clearing lots of pieces.