that sounds more like a pet project game than a fun game, due to how difficult it would be to get used to the mechanics. maybe if you design the art assets right...
that said, this doesnt seem like 4d. it seems more like 3d where your player/units/whatever exists in multiple planes at once.
i have a good plan for difficulty pacing. the use of an extra dimension adds a lot of depth to the once-simple turn based game but i dont plan to utilize the depth to the fullest (if i did most people including myself would struggle to understand it) and even if i do it'll be left for the final levels
an example would be combining switching planes with a gravity mechanic where gravity changes directions. its perfectly possible and could possibly work if i utilize it on a small simple level, but for the most part i cut that idea out because it would be way too difficult to have to brown townyze 3 planes at once AND brown townyze the pattern in which gravity would change
maybe if you design the art assets right...
everything is placeholder right now. im not going to design assets and art until i have the solid mechanics nailed. but dont worry, i have an aesthetic in mind, mostly in level assets, that will look good. it'll be like this
not copying it exactly but i do want to design ancient castle-in-the-sky like greek architecture with gravity defying fountains and stuff like that
that said, this doesnt seem like 4d. it seems more like 3d where your player/units/whatever exists in multiple planes at once.
its not 4d in the context of the universe, its technically 3.5d because a truly 4d game like this would take place between the inside of a tesseract and you'd have to manage 6 planes at once.
consider it 4d mathematically. all the map data would be stored on a four dimensional array. the x and y axis is the 2d axis, the z axis is the 3rd axis, and the t axis would be the 3 planes. every successive axis is basically duplicated as you get to the higher dimension. in this game, you have 3 3rd dimensional playing fields which if i utilize correctly can make the game fun
advance wars actually did the extra dimension subtly with the use of land, air and naval units. they each exist on a 'dimension' in the game, naval being the lowest, land being the middle and air being the highest. and they also are able to interact with each other, such as battleships attacking land units, or anti air attacking air, bombers attacking land and sea, etc.
thats kind of what i want to expand upon, but instead the naval and air dimensions have their own terrain and restrictions that must be taken into account. your units 'interact' across all three dimensions enemy-wise but terrain wise, they can only interact with one at a time, which alternates