In part one of a series of posts about optical illusions on the web, Dan Wilson looks at how to create the “Red Reveal” that he happens to describe like this:
Growing up, my family played a lot of board games. Several games such as Outburst, Password, and Clue Jr. included something that amazed me at the time — a red lens and cards with some light blue text that was obscured by a myriad of red lines. When you put the red lens over the card, the text would magically appear.
Here’s one example of that effect from a nifty Pen:
I’d also recommend reading part two in this series, Barrier Grid Animation, which uses a bunch of CSS techniques to trick your eye into seeing an animation of several static images.