Okay, so I technically have a second thread open with another idea right now, but I just got a really good (I think) idea that I want to do right away if it's not too similar to something else, so here it is:
There is a large parking lot to an abandoned sports stadium. It is slightly overgrown by plants. Half of it, considered the "Lower Half" is blue. On the lot are various drawings of fish (and other aquatic life) and birds (and other flying lifeforms), many but far from all of which roughly correspond to real species. These drawings move freely, and comprise a 2-dimensional ecosystem. Some of them can eat each other.
They interact with features of the parking lot such as concrete islands, the drawn lines which define parking spaces, and, of course, the stadium itself. None of the animals may pass through these features, and the birds will sometimes perch on them.
Creatures regularly pass "in" and "out of frame," swimming or flying right outside the parking lot's edges, or entering from them, implying that this is merely a window to a larger ecosystem.
In addition, it is possible to draw in new organisms with your own chalk and add them to the ecosystem. If you draw a population of fish of a species you just invented, they will swim out of the lot and them or their offspring might swim back into view. You can also kill organisms by washing the chalk off. Rainstorms often clear out the area for a while.
The article will end with an incident report in which a massive object eclipses the entire sea side of the parking lot. At first, the foundation doesn't know what to make of it, but it becomes clear that the object was actually the top of the eye of a gargantuan fish.
Could I get some feedback as to this? Does something too similar to this already exist?