We built a planet out of a cube, and it only has eight problems
An icosphere looked like the obvious shape for a planet. It fell apart the moment real pieces had to land on it. A cube wrapped onto a sphere turned out to have exactly eight weak points — and all eight were fixable.
The first version of the planet was an icosphere — the usual way to turn a sphere into triangles. It looks right in a screenshot. It falls apart the moment you try to drop a falling-blocks piece onto it: real pieces are made of squares, and a triangle grid only has three-sided cells to offer.
What the icosphere actually measured as
Before throwing it out, we measured it. At a reasonable subdivision level, the latitude bands held anywhere from 5 to 530 cells depending on how close to the pole you looked — not a small variance, over a hundredfold. The base shape's own face list was malformed, with 15 of its 20 faces wired in backwards, and cell sizes varied by a factor of 2.4 across the surface. And fundamentally: only three tetriamond shapes exist, so there was never a version of seven real tetromino pieces that was going to sit cleanly on triangles.
A cube, pushed out into a sphere
A cube has six faces, and every face is already a grid of squares. Push that grid radially outward until it's a sphere, and you get real square cells, real 90-degree turns, and rings around a pole that are exact, not estimated, because they fall straight out of the geometry (every one of them is checked by an automated test, for planets from 4 to 12 cells across).
That warp is a real cost, and a mild one. The other cost is not mild: a cube has eight corners, and at each one, three squares meet instead of four. Every other cell on the entire planet has exactly four neighbours. Those eight corners don't. That single structural fact turned out to be where almost all of the hard problems in this game actually live, not the sphere, the corners.
Looking down, not sideways
The camera looks straight down at one pole, so the pile is always on screen and spinning the world is the sideways move. A sphere normally hides half of itself from any single camera angle; here that's covered by a radar, a flattened map of the whole planet, rather than by ever cutting to a second view.
Why the middle isn't empty
A completely open bowl drains every piece straight into the 4- and 12-cell rings right at the pole, too forgiving: the bot sweeps showed it clearing almost every single piece. A fully solid cylinder up to the middle is a shallow band that tops out no matter how slowly pieces fall, too cramped. The planet that shipped splits the difference: a 16-cell solid core and a tall sky above the play area, both plain numbers in the URL (core and top), chosen from bot data, not a guess.