Thanks for playing!
I know I already responded on Discord but I'll re-reply here in case any others encounter the same thing: AP can be restored by blocking an enemy's attack (use Z key to block - X on a 360 gamepad, Square on a PS3 gamepad) and then immediately chaining an attack. You can also chain an additional 3-hit combo onto that counterattack and gain even more AP back.
Item drops and consumable item use is being considered for a future demo however (in addition to more varied enemy types and behaviors)