Thursday, March 22, 2012

Clingstone-Freestone: Triumph & Disaster

Clingstone-Freestone came to me in a flash of inspiration, a fully-formed idea for a puzzle that could be built to resemble a ripe peach with a wedge cut out to expose the stone.  It seemed like a nice idea, but would it work?  Yes, it worked on the first try...but no it didn't turn out a good puzzle.
The premise?  The inner sphere must be correctly positioned to allow two halves of the outer sphere to move freely.  Then the two halves would un-hinge to rotate apart around an axis located un-intuitively at an imaginary point on the missing 'slice' of the outer sphere.
The inner 'stone' is a sphere divided into 3 pieces: one smaller piece with two-axis mirror symmetry, and two congruent larger pieces whose outlines look like continuations of some curves of the smaller piece.
But inside, the larger pieces exhibit two distinct bisecting geometries: a revolution around an imaginary point in the upper half, and a helical slice through the lower half.  The cuts are arranged so the outlines meet seamlessly on the outside of the sphere, thereby disguising the internals.
When the cavity is empty, the outer shell be put together and taken apart without any interference.  But if the 'stone' is installed, the parting lines block it from being disassembled in the same style a Bram Cohen's Cast Marble or Vesa Timonen's Tangerine puzzle.
Only a small part of the 'stone' is visible at any given time, so it takes a lot of maneuvering just to figure out the outlines of the cuts...let alone guess at the internal shapes.
Even after the user guesses the shape and orients the 'stone' correctly, it's still a bit unintuitive to open the puzzle because it unhinges around an axis outside the surface of the puzzle.  It won't disassemble unless the user gets the right motion.
Another unintuitive detail, the disassembled puzzle is very asymmetrical.  The smaller piece of the stone comes out with one of the halves, while the two identical pieces remain cradled inside the other half.

So far, the mechanism seemed to work perfectly on the first (and only) prototype I built.  But the whole premise has an intrinsic flaw....
In some orientations of the stone, there would be nothing to prevent the smaller piece from being extracted through the opening.
Removing the smaller piece not only permits the user to see the inner workings of the puzzle, it partly-resolves the obstruction.  Although it's still somewhat challenging, it doesn't work as I'd intended.

Wednesday, March 7, 2012

Cooksey's Griddle

I finally managed to build my Cooksey-inspired flat maze on the SD300.  My last build failed because I'd been using a worn cutting knife, and this model packs a whole lot of cuts into a very tight space.  I put in a new, factory-calibrated knife shortly before building this model.

I'd used three colors by switching materials between the major areas of the puzzle.  That yielded a surprise bonus because unused material was consequently color-coded to easily distinguish the difficult middle section.

I had programmed SDView with an elaborate scheme of peeling cuts to ensure the middle layer could be cleared from the outside, but I'd still overlooked a design detail.  Consequently, a lot of the material had to be freed by tediously tugging pieces of material sideways before pulling it out through the openings.

When the puzzle is fully assembled, the shuttle rests in a grooved handle.  The side walls keep it securely nested in the handle.

A disc at the bottom of the handle prevents the shuttle from coming off at the end, so the only path to remove it is to slide the shuttle into (and through) the maze.

The tab on the shuttle only allows movement along one axis (vertical) when it travels on the red side.  Horizontal  movements are blocked so long as the tab rests on the red-side grooves.

Another tab can be pushed into the blue grooves on the flip side of the maze.

Engaging the tab on the blue side disengages the tab on the red side, so horizontal movement is no longer blocked.  This allows the shuttle to move left & right as far as the groove on the blue side permits.

The user navigates the maze by alternately engaging the tab in the blue side for horizontal movements and engaging the red side for vertical movements.  Neither side exhibits the actual maze, so the correct path is not apparent.

Eventually the shuttle emerges from an opening near the start of the puzzle.

The shuttle is still hooked over the puzzle's handle, but now the tabs aren't locked into the grooves in the handle.

This arrangement allows the shuttle to spin around on the handle so the tabs move to the other side.

Now the shuttle can re-enter the maze, but with the tabs on opposite sides from before.  Now the horizontal movements occur on the red side and vertical movements on the blue side.  It's a completely different maze, without any similarities to the first.

By navigating through the mazes as shown, the user can eventually remove the shuttle through an opening at the top of the puzzle.  Naturally it's not quite as simple as it seems because there's still a subtle subterfuge or two.