The towers go up, the towers go down – that's the flow of the game in Ka-Boom, and whether you want the towers to stand or not depends on whether you're the master builder for the round or a saboteur aiming to cause destruction.

At the start of the game, players lay out the 26 tower tiles, with one large tile in the center of the playing area and the remaining tiles placed randomly around it. Each tile depicts a stacked arrangement of blocks as well as a point value. On a turn, the master builder takes the sixteen tower blocks, flips the sand timer, then starts building whichever towers he wishes, with each tower being built on the tile that depicts it. Each other player is a saboteur and has 2-10 ammunition dice that she tries to shoot at the towers with her catapult (which is more like a tiny teeter-totter really). If she knocks over a tower, great! No points for the master builder, although he can use the fallen blocks to rebuild if time remains. If an ammunition die lands on a tower tile, the builder can't build on this tile; if he's started building on this tile but hasn't finished, he must stop and move elsewhere.

If an ammunition die lands with the "Ka-Boom" symbol face-up, nothing happens. However, if a second die shows this symbol, the player who shot this die gets to slam her fist on the table once; if the ensuing earthquake knocks over towers, too bad for the builder. One player has a giant ammunition die, and this can cause an earthquake all on its own, but saboteurs can't cause more than one earthquake a round.

When the sand timer runs out, the master builder claims any tiles on which he has correctly built a tower that still stands. The next player in clockwise order then becomes the new master builder. As soon as a player reaches 16 points, the game ends and he wins!