Nice work! Reminds me of the Minesweeper on old Windows I was playing to when I was a kid.
Projects with siblings are the best!
I do not know how you could extend your project. I saw minesweeper clones with more exotic geometry such as hexagons or in 3D with a cube or a sphere but that's a lot of work for little added value in my opinion. Or you could try to add new tiles, or write a story with different levels, or make a level editor, or improve procedural level generation. But in my opinion, it would be more valuable and instructive to start a new project, maybe one with real-time gameplay, such as a snake clone or a breakout clone, to see different techniques.
By the way, I laughed when I saw this function name "setNeighbombs", good pun!
