I'll let Lollorcaust (or anyone else) work on the improvement.
Here's the 20-second TAS I was referring to:
http://tasvideos.org/userfiles/info/2491746511994026
Up until the final boss, my TAS is slower by 1 second, but saves 6 seconds at the final boss. The improvement is as follows:
- First, shoot one of the center blocks.
- Then, go to the left and shoot the three blocks on the two columns at the very left.
- Now, shoot the blue moving barrier at the leftmost column and immediately for the next shot shoot the blue moving barrier at the second left column; since the dents in the blue barrier move, the second shot will hit the dent made by the first one and create a hole allowing a well-timed shot to pass through completely.
- Finally, return to the center and shoot all the center blocks and then shoot the alien through the moving hole; there is just enough time to do so.
The center block is a bit strange. Shooting just right of center clears a block of width 2 along the center, whereas shooting just left of center doesn't clear any blocks, but by shooting it enough (about 8 times or so), you can form dents and holes in the blue barrier even without clearing any blocks. The blue moving barrier also treats the center as width two. It seems like a programming bug to me.
The bird-like enemies in the third and fourth areas have confusing movements, so if anyone wants to figure out how they work, then good.
Finally, please don't let the player die to the final boss's shots at the end. Just use the shield if you have to. Also, it is probably a good idea to stop the encode a bit after when the game returns to the first area (maybe a second after) so it is clear that the final boss is actually defeated.
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Edit: The center block bug seems to be an emulator bug, since
this Youtube video indicates that the bug should not occur during gameplay.