Just an idea.

Running from left to right:

MP Crystal: Consume to restore MP. Used for Special Attacks.

Agility Crystal: Consume to restore Agility at a faster rate. Used for Double Jumping, Dashing and Jumping/Dashing Attacks.

HP Crystal: Consume to restore HP.

Basic Attack: Swings the players sword. The sword attacks can combo based on the level of the sword.Capable of upgrading as the game progresses 

Block: Raises the players shield to block enemies projectiles. Can take a limited amount of hits before it breaks. Capable of upgrading as the game progresses 

Special Attack:  Dependant on Special Attack Pickups scattered through the game. Each one can be upgraded as the game progresses. The one showed is "Flame Spitter", which sends fireballs to rain down on an area in front of the player