Love the lighting in that screenshot, and the expression on our hero, what a determined little guy
Do you think the game should warn the player for each new wave?
Ooh, there’s an interesting question!
In a shoot 'em up I’d have gone with yes if it was a case of surviving wave after wave after wave. Your RPG, in my opinion, doesn’t feel like that though, it feels more about exploring and collecting, and a bit of battling on the way whilst getting to an endpoint, before moving on to the next area.
Would the player be aware of the increasing difficulty, enough to think, “hmmm, I need to get out of here”? I’m guessing they would be aware of the increasing experience/higher levels of just playing.
I think if you have only a message appear “Next wave…” it wouldn’t work, I’m not sure if you have other modals pop up for notification other than the inventory at the moment?
In Plants vs Zombies, for example, you get a little sound effect, “The zombies are coming…”, perhaps a few varying sound effects saying similar things, “Oh no! More enemies are approaching”, “Seriously, more skeletons!”, “I see dead people!” and so on, that could indicate, perhaps more subtly, a start of another wave of enemies, but without specifically referring to that event as a “wave”. It may help maintain the light-hearted/fun style that the rest of your game mirrors.
Of course, if you were going to have a game mode that was pure survival, for a selected level (could be fun), then indicating the next waves, perhaps via a similar modal to the inventory, would work really well.