NEW: Game trailers are now being shown on game pages, in HD (yay!)
Just click the preview image in the sidebar. (And yes, I pretty much reserved the sidebar for trailers long ago... Was just too lazy to get the app IDs for said trailers.)
The list is being generated right now, it'll be done in about a week, I estimate.
On Firefox and Webkit/Safari/Chrome, you'll get an animation when clicking the trailer preview.
On Opera (Blink), the animation was disabled because Opera shows a stupid 'detach' button that is drawn through the Shadow DOM, meaning I can't hide it.
On mobile browsers, the trailer window can't be moved.
On Firefox, you can move a trailer by dragging the black background below it. (Which is the main reason I have some text there.)
On all other browsers, you should be able to drag the entire video, including by clicking and dragging the video itself.
Click outside the video to close it.
It took me an entire day to build this, mostly because of the browser bugs mentioned above that forced me to try various things to fix them. (I failed, obviously. But it's better than nothing.)
Note that I'll eventually support trailers & images for all Steam games. I just need to finish my updated API scraper.