It's raining since a few days at my place. And even though it actually just stopped raining as I'm writing this post, the sun hardly comes out anymore. It's autumn on the northern hemisphere. The chances of seeing what is probably nature's most colourful phenomenon this year are close to zero. What a pity.
But there's a remedy: Let's just build our own rainbow with JavaScript, some HTML and some mathematics! And no, we're not using any built-in linear gradient functions or CSS today.