Pen sketch on paper, colored digitally.
The dodecahedron (12 pentagon sphere-like object) is a little wonky, as is the turtle tessellation page. Other than that, I'm sort of happy with this piece. The coloring is a bit simplistic, and the water's near-realism doesn't quite match the sketched part's unrealistic hand-drawn quality, because I was a little rushed.
i will probably try to sell the original black-and-white pen sketch on eBay. Alternatively, I may try to color the original with watercolors and THEN sell it.
This poster will be appearing in a newspaper ad (B&W), in color as a poster, and in pale greys as a memo pad souvenir given to attendees.