How do I Shoot Em Up?

The past 2 months I been trying to build a simple horizontal shoot em up game like Gradius. Working on general mechanics and testing 2 different types scrolling. My real question is, what scrolling is more common to use in horizontal shoot em up games like Gradius.

1. Using the system scroll x and parallax layers? (where the window is moving thru the long layout)

or

2. Having star field and Objects scroll -x with loops. ( window doesnt move, objects fly horizontal across the screen, illusion that is moving)

Another question about option 1. Option 1 would require to have a large horizontal layout maybe having 20000 px in size. is that normal for most games to have a huge layout?

Hope this isnt hard to understand. Would really appreciate any feedback or tips.

JasonS

I think the best approach would be to have an infinite scrolling background so that it gives the illusion of constant movement horizontally. That way you would not need to have a large layout.

Firing several shots at the same time think that consumes a lot of memory, I think it is more appropriate to create a sprite shot that sits at the edge of the ship and along resize the sprite to the collision with the enemy object if there are no enemy arrow size for far if you can see the shot on the screen.