The scenes need to be small enough to load quickly and not lag during gameplay. They also need to be big enough to explore and fit interesting content. A nice trick to making a place feel bigger is to zoom in on the avatar, limiting your view and even feeling a bit claustrophobic indoors. I can use this trick for some parts of the game but for others, it's important that players can see far.
Particularly in battles. This game plays like a shooter so you need to see where projectiles are going and where they're coming from. There will also be puzzles where a larger field of view will be necessary, so I coded the game to adjust the camera and HUD as the zoom changes dynamically. It's a useful rick I'll be putting to use in fun ways once I have some maps planned out.
Right now I'm doodling ideas for a contained area to work on graph paper. The tile room in the collision test video was the base for the forest battle scene. All the battle rooms were going to be like Kingdom Hearts Re:Chain of Memories (PS2) where the rooms are blank and the enemy behaviors are the main attraction. I also like how escaping battles in that game is done by running toward the edge until a bar fills up.
After some consideration I decided to make things a bit more interesting. When I got the collision working I realized that my fear of coding pathfinding was unnecessary. I'd have to make it so they behave in the overworld anyway. So now I'll have to think up ways to make each region's arena feel unique and fun. I can also think about designing the local enemies to work well with their landscapes. I can also make special rooms for each boss fight.
As for common enemies, I plan to keep my idea for randomized terrain breakables and hazards to help battles feel fresh each time. There will simply be landmarks that are constant.
The overworld maps I'm making for tests are going to be a plains area, a forest clearing, a Zelda NES lost woods area, and a small town. That should be enough room to try out nearly everything needed for my next milestone.