Crystals and new weapons are often hidden off the main path in each stage.
The game is primarily for PC but can be played on Android via specialized setups like Winlator or specific Wolf RPG engine configurations. Rignetta's Adventure | Full Gameplay Rignetta’s Adventure [Final]
If a boss is too difficult, the game allows you to "push by" them and continue exploring to find better gear before returning. Crystals and new weapons are often hidden off