If you've used Photoshop or basically any other image processing application this century you've probably come across the concept of blending—mixing the colours of two layers beyond what's possible with opacity. You may also be vaguely aware that this feature has made its way into most modern browsers, but why is it useful?

If you're like me, you might assume that these effects are only useful for images, and, even then, only for the kind of dramatic effects that look good in a tech demo but, frankly, seem out of place in building products or pages day-to-day.

But blending and compositing (the subject of the next episode) is much more than that. It's a gateway into an internal browser process that completely changes the way a website gets displayed. And gives us an incredible potential for rich, performant web designs that haven't been possible before.

For this episode, though, we're going to make sure we understand the mechanics of what's going on. And answer the question—what kind of blend modes actually produce something that looks good?