It's good

but, if you're looking for this to be a "dark" track as the title suggests, try some instrument(s) or lower-level sound of some sort, something that will give it a lean toward a hidden evil feeling, if you know what I mean (I don't speak tech/studio-language at all, so I'm trying my best to put my words together). Basically, if I had a "dark side" to my happiness, I'd be wearing an invisible evil grin; so I guess try imagining an evil grin while working on it. But I don't think it's that repetitive. Good work so far!