Poseidon's Cube started out as a novella. A very long winded and fluffed out novella. The anthology was a great challenge to streamline and strengthen the story. So, I bled my fingers cutting out the frivolous points, mercilessly killing two subplots, and then revising the middle and end to align better with the anthology's wants.
The end result is something I'm very proud of and the second real short story I've written. It took quite a while for me to understand the mechanics of short story writing and Poseidon's Cube was like an applied exercise.
Here are my thoughts on short stories:
Length: 2,000-10,000 (varies by publisher and targetted market)
Plot: Usually a single event with few scene changes
Characters: Small. Recommend no more than 5, and that's if they are involved throughout the whole story. If the MC is going to meet characters along the storyline, have it early and less than 4 characters...maybe 2 or 3
KISS (Keep It Simple Silly): You don't have a lot of words so cut out anything unneeded. The sentences should be tight and impactful. Make each of them count.
Surpringly to me, I believe short stories are what jumped my writing development. It challenges and teaches you as the writer the essential ingredients of your story. You might try it and see what you come up with.
Let me know how it goes and good writing to all!