assignment3 (shangyu xie)

This is the first time I have tried to make a shooting game. I tried to imitate the professor's style. The player can fly the spacecraft, and there are three lives. The enemy's spacecraft is randomly generated. If the player encounters the enemy, he will lose his life. When his life is exhausted, the player will die. But in this project, I haven't added the beginning and end scenes. I will join in the next mission.