An empty carton used as a shelf extender between the window and the fridge

I got this box of instant noodles (6 cups, 0.5PLN per cup, 3PLN total) on sale (this brand tends to cost 9PLN/cup) cuz it was nearly expired, with no plans on what to do with the box itself. Today my flatmates noted my stuff is sprawling too much, so I looked at the box, and just… Placed it on that windowsill right next to the fridge. And sure enough, it pushed back my stuff quite a bit, so it doesnt extend past the fridge anymore.

It might not be the prettiest shelf extender, but it sure does the job, lol

I'm kinda tempted to expand it vertically, but no idea how to deal with that… I have some larger empty cartons I could cut up, but it's hard for me to gauge how sturdy that shelf would be.