- Music and sound effects, which are queued up and loaded in the background (it's even possible to play the game with missing music and SFX, and you'll start to hear them once they've loaded).
- Google Adsense content. This ticks me off because some of the ads are very poorly behaved. Some load relatively large amounts of content, and can often block page loading. I've therefore pushed the Adsense script itself right to the bottom of the page so it doesn't result in other requests from the game being blocked. I'd vastly prefer it if Adsense restricted ads to plain text or simple images, banning active content and Flash (which, at least up until recently, was still appearing). The reason for the ads is I need to cover the costs of the site, never mind actually earn a living, but I want to do so in a way that doesn't detract from the player experience.