The original Spelunky is released for free back to 2008, 8 years ago by Derek Yu (@mossmouth). But even now, it's still the perfect title to study the concept of roguelike. Especially the way of using random level generation (PGC) made the game really stand out. The book explains why game designer makes certain decisions at some points, you will see the interesting fact that game design is both a science and art.
Duckey
Master Expert