That took a while...
It took a while until my mind understood that the tank is really infront of the people. Of course the hints are clear but my mind insisted on seeing it standing next to them. Things closer to the viewer have a higher contrast, once you get that it's so obvious that you can't see the tank next to them anymore. And of course, the fact that the grass is behind the tank is a good hint too.
Usually I would say you could move the tank a slight bit down so it's easier to make out that it's in front, but I see how the composition is so important and so strong in this piece that moving the tank might be a problem.
It took a while until I got what's going on overall. At first I thought 'Ok that's Pico and Nene in the back... probably... and the one guy wears Tankmen glasses... but who are those other two?'. And judging from Izzy-A's comment I am not the only one who asked himself that question. But then it struck me like a lightning bolt.
OF COURSE they represent the four portals! Guy listens to music, girl is an artist, gamer controls the RC tank and the other girl is filming it. Now that I got this this, I like your drawing even more. Trust me, I am not the only one who didn't get it, so it might be a good idea to give a bit of an hint towards it in the author comments. Although the title is a good hint already and helped me understand it.
Before I got the concept, I already loved the art. The color scheme is a pleasure, it's well composed and of course, it's very well drawn.
It also works good for an autumn month for the calendar, that was a nice decision and implemented persuasively.
Good luck for the contest!