This is an editor for two-dimensional programs made of glyphs, each of which has an alias (plaintext name) and an effect. You can click on a cell in the grid to change (or clear) its glyph. The current program is stored in the hash fragment of the URL, allowing for easy sharing and undo/redo.
Program execution is controlled by a cursor, which starts at the top left cell and moves to the right, executing each glyph it passes over. Some glyphs change the direction of the cursor, facilitating control flow, while others modify the stack or perform I/O.