The goal of each stage is to move the
◯ to the
◙ using or . Oftentimes, the player must move their
◯ into a
■, which displaces the
■ by one block in the
◯'s direction—more simply, it "pushes" the
■. Like most shapes,
■s are solid, and cannot be pushed through walls or through other shapes. Moving
■s and their variants makes up the bulk of the gameplay.
► all have points that are harmful to the touch, but these shapes too can be pushed from their flat side. On the other hand, a
◆ is hurtful all-around.
▢ shape is a flimsier type of
■ that can be pushed indirectly. Pushing something into a
▢ with space behind it will push the
▢ as well. This is a trait unique to the humble
◙ will be broken in two, and the player will have to push a
◛ together to put it back together.
Later levels introduce
▤ can only be moved horizontally, whereas a
▥ will only move vertically.
The player can press and to undo a previous move and to redo a previously undone move, respectively. Unlike most block puzzles, all actions—including undos and redos—take only a quarter of a second (15 frames in the expected 60FPS) to animate, to avoid player boredom and frustration.
If the player is truly stuck on a puzzle, they can pay in Play Coins on the pause menu to get up to five hints.
Despite the overall colorful, abstract presentation, several messages hint at something greater, appearing written in an alphabetic shape-based cipher.
- Stage 16 contains a large message, made using
▢s as effective pixels and transliterating to weverebuilt. The player must move many of the shapes to continue, destroying the message.
- In Stage 23, several shapes placed to the right of the area form an apparent paragraph, the visible part of which can be read as seodenonesohcehtlitnusevomgnihtonsarellitsnee. This would normally be off-screen, so the
◯must deliberately move to an empty section of the level to pan the camera over. The same "paragraph" can be seen from the upper-left of Stage 24 in a similar fashion; the remainder reads wtebetirwewekorbwolfemitruo when deciphered.
- The intended solution for Stage 29 involves moving three groups of into
■into larger shapes. From right to left, these shapes transliterate as you.
- Stage 35 contains groups of shapes explaining the transliterations of letters E, T, and R. These factor into a puzzle later in the stage, but can also be used to decipher earlier and later messages.
The stages are designed such that the player is silently introduced to new mechanics before seriously needing to use them. Typically, a stage introducing a new shape will require the player to interact with it early on, to be followed by a stage using both the new shape and an old one the player is already used to. Later comes a stage where the player must use the new shape in conjunction with several familiar ones, requiring them to use implied inherent properties of the new block to solve the puzzle.
Stumbling Blocks plays its learning curve very safely. For instance, Stage 1 does not include any shapes, such as
■s, or puzzles to be solved. It is a flat, rectangular area with a
◙ out in the open, waiting to be interacted with. This is just one example of the game's minimalistic design.
Despite the careful level design, some stages contain areas where the player can manipulate the puzzle into an unwinnable state, though this can be undone by undoing any number of moves.