Hmm - how reliable have you found your alpha fullscreen rectangle?
Technically you are not guaranteed to get the same backbuffer preserved after you do a Flip(). The o/s might allocate several back buffers and cycle through them, or you might not even get one. Assuming that its contents will be preserved is nice and efficient but I would expect that on some systems the screen will flicker and swap between out of date images, or show old unwated graphics.??
The safer way would be to render to a texture and keep the texture.
How are you doing your collision detection between the player ship and all the enemies/bullets?
Technically you are not guaranteed to get the same backbuffer preserved after you do a Flip(). The o/s might allocate several back buffers and cycle through them, or you might not even get one. Assuming that its contents will be preserved is nice and efficient but I would expect that on some systems the screen will flicker and swap between out of date images, or show old unwated graphics.??
The safer way would be to render to a texture and keep the texture.
How are you doing your collision detection between the player ship and all the enemies/bullets?