As a greenhand at independent game field, I am curious about how to design a game. As for me, well, my favourite game is the binding of isaac. So when I try to imgane a model I want to adopt to my game(still in plan yet), I always fell to a *Isaac-like* model (you know what I mean). I am wondering how to expand your ideas for designing game modes
Playing more and different games is always a good option. If you want to really have your eyes opened, grab an emulator and dig into earlier generations of games; there was a lot of experimentation in earlier eras, and a great deal of it has been forgotten. There’s some wild stuff in the dark corners of the Commodore 64 (eg: Paradroids) and PlayStation 1 (eg: Carnage Heart), for example. Both of those hold up well even today.
More generally, try to avoid the trap of “this game I like but with this one problem fixed”. It tends not to lead anywhere interesting.
Try taking ideas from different games and see if you can make them work together, at a scale you can handle yourself or with whatever team you can assemble. You could ask yourself something weird like “what would Binding of Issac look like as a turn-based metroidvania?” and see if you can come up with an answer that makes sense.
The other big trap to avoid is having what you think is a full game design but is actually only a “wouldn’t it be cool if ______?” thought that collapses under the weight of any real observation. Put ideas down on “paper” (real or digital) and try to flesh out a description of what the player does, how they do it, what the controls look like, the story (if any), the player’s goals…
You can do that concurrently with some of the early building, but you really want to have some semblance of a complete design before you start committing yourself to implementation decisions that are hard to undo.
It would help to read some books on game design. Ultimately your game should have good gameplay. Everything else is extra. A great story is nice, but not necessary in all game genres. It’s nice when a game looks and sounds good too. But if a game isn’t fun to play, then there’s no point.