Sorry to say, though, it behaves more like a free drum machine app you use once, then delete.
In a way, the "H.S.K.T." site wants to be an in-browser game, with sandbox elements and flashy visuals. But the controls simply aren't intuitive enough for it to work as one. Granted, plenty of games throw you headlong into the action and let you figure out the controls as you go, but there are conventions—W, A, S, D as movement keys, space as the action button. The combination isn't arbitrary, either, but instead puts your left hand almost exactly in home-row position and keeps your hands from crossing unnecessarily. Think of it as the analogue for a pianist's proper hand positions.
So while space does start the beat on this site, the other controls seem arranged haphazardly. Many letters trigger synth tones and geometric blooms, while the top row numerals summon video snippets and Amelia Meath's vocal. Try and control the track with one hand and the vocals with another and your hands inevitably tangle—something avoidable had the designers followed basic computer game conventions.
But maybe that's not the point. Maybe this is supposed to be a drum machine or sampler. After all, each key does trigger a sample. Yet the sheer, stylish opacity of the interface renders it lacking there, too—no way to remix a song, really, if you can't see where the beat even starts. More often, you end up with Meath's chants looping out of time and in a different key from whatever synth sound you've discovered. With a little practice, you can get a rudimentary backing track going, but it's tricky to get the vocals to lock, too. And the beat itself—that thing people take to samplers or drum machines to construct in the first place—gets repetitive fast.
The trouble here is that hskt.co wants to be a drum machine, a sampler and an in-browser game, perhaps all at once, but it is too opaque as an interface to succeed as any of those—a good idea, then, too hobbled by coolness to be user-friendly.
In other, more positive Sylvan Esso news: Check out Amelia Meath's recent track at annotations at genius.com. They're great.