The gameplay is similar to that of old school nintendo games like Castlevania, in a sense. You start a level and travel from screen to screen, each screen having having a unique challenge or set of obstacles. After about 4 or 5 screens in a level, you will reach the boss. If you successfully beat the boss, you continue to the next level.
Some of the challenges consist of clearing a room of monsters before proceeding, surviving a scrolling stage with a spinning blade on the bottom of the screen, figuring out an electric cube placement puzzle, etc. The biggest challenges will of course be the bosses, who are each very unique in how you accomplish defeating them, similar to Zelda. Expect to die a few times before you figure out the correct strategy in beating them :)