Continuing with the 8 bit fascination, the Sierra game engine from those days was quite impressive.  It had static bitmaps for rooms, collision objects, Z buffering, & player animation.  It used vector graphics.

Young lion envisioned some mix of scrolling world & static rooms for his Robotech game.  A scrolling world would have been quite unplayable, in the end.  Truth be known, the signature graphical Sierra adventure games never supported the C64.  They were all on x86 & apple II, using plain bitmap writes.  Kiwipedia clearly shows the C64 wasn't supported.  https://en.wikipedia.org/wiki/Adventure_Game_Interpreter

Their most advanced games for C64 just had non interactive, procedurally drawn graphics as illustrations.   Their most advanced C64 adventure game was Mickey's Space Adventure.

They made a formal game engine for x86 & apple II starting with King's quest.  It had a very small player & very few occluded zones.  The mane mystery is why they didn't do the same on the C64.

They all drew the graphics in place.  It was a 160x150 graphical area with a 30 pixel tall text area below.  It seems to have dropped 20 pixels from the top & bottom.

This room is using an alpha mask to draw the chain on top of the player.  A C64 would have to use sprites for the foreground or just draw the whole thing in bitmap RAM.

As usual, the hardest part would be creating the assets & plot.