The blue circle is the "crosshair", you can interact with the barrels if it is on them. Though after eating 2 of them the character is too big so it is near-impossible to interact with the rest of them or with humans.
oh, ok! I thought that might be the case, but I just thought it would need to be near it, not actually on the barrels. I should have tried that but it's a bit hard to control the blue thing precisely. I'll give it a try now, thanks!
