I just discovered you can play a full game of Tetris right inside a PDF document. The PDF is plaintext and works in most desktop browsers that support PDF.js or PDFium.

• Use the arrow keys to move and rotate the Tetris blocks.
• WASD acts as arrow keys in the input box
• When the game is over, you can save your score by printing the PDF page.

Game creator: Thomas Rinsma

GitHub repo: pdftris

You can play directly with this link.