Beach Tic-Tac-Toe in a Scallop-Shell Box — Sea-Creature Peg Game (starfish vs shells)

Beach Tic-Tac-Toe in a Scallop-Shell Box

A pocket tic-tac-toe you can actually play on the beach, packed inside an openable scallop-shell box. The pieces are little starfish and scallop shells that plug into holes on the play field — a snug friction fit, so a gust of wind won't scatter them the way flat tokens blow away.

How it works

• The lid is the play board — its inner face has the 3×3 field: 9 holes + an engraved # grid. Lift it off, turn it holes-up, and plug pieces in to play.

• The base is a plain storage cup — no holes, so the loose pieces can't fall through or spill. Closed, the lid's holes face down into the cup and seal everything inside.

• Starfish ×5 vs scallop shells ×5 — equal counts, so whoever starts, both players hold a full set (no swapping pieces around).

• Pieces press in and pull out by hand, but stay put once placed. A thumb scoop at the wide edge pops the lid off.

What you print (all flat, no supports)

• tictactoe_shells_base.stl — lower scallop valve = plain ribbed storage cup.

• tictactoe_shells_lid.stl — upper scallop valve = the play board (ribbed shell outside, 9 holes + # grid inside).

• tictactoe_shells_stars.stl — 5 starfish pegs.

• tictactoe_shells_shells.stl — 5 scallop-shell pegs.

Print the two peg sets in two filament colours so the players are obvious — and the base/lid in two colours for a two-tone shell.

Fully parametric — the included tictactoe_shells.scad exposes the shell size and rib count, the wall/floor, the hole pitch, the peg post/hole fit (post_d / hole_d) and the lid slip-fit (clr). Tighten or loosen the fit for your printer, or scale the whole thing up for bigger hands.

PLA is fine for a quick game; PETG holds up better to sun and saltwater.