首先，尝试添加变量 dx 和 dy 来存储键的状态

As a first go, try adding variables dx and dy to store the state of the keys

           elif event.type==KEYDOWN:
                if event.key==K_w:#moves banshee up if w pressed, same for the other WASD keys below
                    dy = -5
                elif event.key==K_a:
                    dx = -5
                elif event.key==K_d:
                    dx = 5
                elif event.key==K_s:
                    dy = 5
           elif event.type==KEYUP:
                if event.key==K_w:#moves banshee up if w pressed, same for the other WASD keys below
                    dy = 0
                elif event.key==K_a:
                    dx = 0
                elif event.key==K_d:
                    dx = 0
                elif event.key==K_s:
                    dy = 0

    x += dx
    y += dy
    screen.blit(banshee,(x,y))
    pygame.display.update()