Modularity and Performance 

Delving On uses modular tilesets to create the "shell" of any particular level. Levels are designed similar to old dungeon crawlers like Wizardry or The Bard's Tale. 

The more simplistic style of graphics as well as the modularity insure that huge levels can be created in a short amount of time, certainly shorter than if using more common approaches. This means Delving On can be very ambitious in scope even with a small team. And it can look good too. Even though simplistic, the goal is not to dumb down the look and create a wholly stylized look. The goal is to present the levels in such a way that they are quite unique from one another and make the player feel like it is a prize to enter a new area, similar to design philosophies of the 8-bit era.   
Performance is very good and texture memory usage is very low, so it becomes less about fighting against a performance budget and more about making interesting locations. The goal being, the player is excited to explore further.    

Cellar Tileset from Below

Tileset Example

The Layout