Gutwhale is a challenging shooting game set inside a whale. Unusually, you only have one single bullet, which you must continue to collect after each use if you want to shoot again. The game is split into three distinct levels, each with four sub-levels (or rooms). Once all the enemies in any room are dispatched, the floor will disappear and your character will fall into the room below.

The rooms in Gutwhale take on the appearance of a dilapidated building, which seems at odds with being inside the guts of a whale, but part of the charm of the game is in its strangeness, something which is also reflected in the highly infectious techno soundtrack.

Each of the rooms will have different collections of enemies (from jellyfish to floating skulls) each time you play. Also, the layout of those rooms varies slightly too. This randomness makes each run through the game less predictable, increasing the challenge.

To mix up the experience further, your character can unlock and wear a variety of hats. These hats grant different game changing abilities, like being able to jump higher or collect more points.

Between levels you also get the choice of spending the points you've accrued on other hats or other power-ups. Those points can rack up much more quickly too, if you're skilled enough to make good use of the combo system, which gives you a multiplier to your score if you can collect your bullet before it hits the floor after use.