Fascinating, the number of formats out there.  Longshot Island does me the favor to define precise criteria:

Usually stories with more characters work better than stories with fewer characters.

Check. Lots of spiky characters, that’s the easy bit.

 We prefer shorter stories, 500 words to 2,500 in length.

Wordcount feels kind of low, even for shorts. The newbie writer goes search and finds confirmation. Cliff’s Notes provide a range of 1,000 to 20,000 words for short stories. A short short. Why not?

Except there is also this detail of a creative requirement:

We are looking for stories that surpass traditional genres. Slipstream. Steampunk. Subterranean. To name a few possibilities. We are looking for lost places. We want stories that make people laugh as well as cry. We want something different.

This calls for a quick check on Wikipedia.

Slipstream is a kind of fantastic or non-realistic fiction that crosses conventional genre boundaries between science fiction, fantasy, and literary fiction.

Steampunk is a subgenre of science fiction or science fantasy that incorporates technology and aesthetic designs inspired by 19th-century industrialsteam-powered machinery.

Subterranean fiction is a subgenre of adventure fiction which focuses on underground settings, sometimes at the center of the Earth or otherwise deep below the surface.

Interesting business model. Let’s try this and call it the 2k challenge.