The five Platonic solids— tetrahedron, hexahedron, octahedron, dodecahedron, and icosahedron— are perfect geometric solids whose surfaces consist of equal-sized, equilateral, and equiangular polygons. They are implemented here as an interactive application using SVG and JavaScript. You can select a solid, rotate it, color it, and then download it. The Platonic solids are open source.

Platonic solids also make for excellent tree ornaments or fridge magnets. You can find photos of these objects, as well as the corresponding print files, here; they are licensed under the Creative Commons License (CC BY-NC 4.0).

Anyone who's ever waited for a train at a station knows the peculiar behavior of station clocks: the second hand stops at twelve o'clock, waits a second or two, and then starts its next rotation.

You can find out what this is all about and how you can design and use such a clock yourself here. The station clock is open source.

A beautiful and completely useless app: animated triangles.

This responsive application—built as an SVG with embedded JavaScript—overlays a rectangular area with a grid of animated triangles. Colors, movement, lighting, and other parameters can be freely configured. The animated triangles are open source.

A pretty neat idea: digital clocks, created with SVG and JavaScript.

Here you can design your own digital clock, download it, and embed it in a website or display it directly on your screen. The clock is open source.