Turing Tumble

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Turing Tumble is a board game created by Paul Boswell in 2017 to demonstrate mechanical computing.

Board and pieces

The board is a series of several pegs stacked in a grid pattern. At the top of the board are two separate ramps which contain blue and red marbles respectively, of which are dispensed by a marble pushing a matching lever found at the bottom of the board. There can only be one marble running at a time. Every peg in a checkerboard pattern is allowed to have one piece, while every other peg may only hold a gear.

Part	Description	Function
Ramp	A green sloped platform with a curved end and a counterweight.	Causes a marble to be dropped directly onto the tile to the bottom left or bottom right, depending on the orientation.
Crossover	An orange chamber with two funnels and a flat bottom.	Causes a marble to continue moving in the direction it was transported from, allowing paths to cross over one another.
Bit	A blue wedge with two ramp-like curved ends on both sides.	A functional equivalent to a T flip-flop. It points either to the left or to the right; marbles traveling onto it are sent out the opposite end, toggling the direction the bit points towards.
Gear bit	An indigo piece with the same shape as the bit, in addition to a gear piece.	Equivalent to the bit, in addition to sharing state with other connected bits.
Gear	A red gear.	Connects gear bits together, allowing shared state.
Interceptor	A black container.	Catches the marble, preventing it from proceeding further and halting the program.

Computational class

Turing Tumble has been proven to be Turing-complete, given an infinitely long board and unlimited pieces.

Further reading

• https://www.sciencedirect.com/science/article/abs/pii/S0304397523000476

External links

• Turing Tumble kickstarter page with video explanation
• Emulator in JavaScript