One suggestion if I might? I noticed some of the imagery didn't seem to immediately 'grok' with their topics. For example "Sports" shows a photo of a bicycle propped against a wall in what looks like someone's flat, while "Arts" shows a photo of a basketball court, "Animation" showed a photography studio and the "Comedy" topic has a group shot of business suit types (albeit in a 'silly' pose).
It was a little odd, definitely nothing that breaks the platform but it may help 'discovery' to make images a bit less...ambiguous given the topic they're related to? I think sports and my mind goes to team sports and not necessarily riding a bike to work (the image looks like an average commuter bicycle versus a racing bike) so maybe that's on me to make the mental adjustment when assuming the connectedness of topics.
Otherwise, neat idea and service!