Ncku Project3: http://slides.com/hmkrl/2018-pd2-project-2#/
Requirement: * Player can control by human (5%) * Player's HP -1 when hit by enemy, game end when HP=0 (5%) * Player can shoot bullets to attack (5%) * Player can manually use limited-times skill (10%) * Enemy can move by itself (5%) * Enemy can automatically attack (5%) * Enemy lost HP when hit by player, HP must be displayed (5%) * Show player score, you can design your scoring method (5%) * Player and Enemy's class must use Polymorphism (5%) * Demo (50%) * Bonus (Up to 20%)