One issue with the station graphics is the gaps in the image which are used to create a shadow effect. They look great, but play havoc with collision testing. I built a test version, available below, that lets you move a horizontal shot around with the right joystick. It denotes a collision by changing the score to 888888:
If the shot ends up in a shadow there's nothing to collide with, so the score shows 0:
Collision tests are done row-by-row, so I got to thinking that a way to handle that would be to also consider the rows above and below the row being tested. I should be able to fill in the shadows by ANDing the above and below rows together then ORing that with the row being tested. In pseudo code that'd be (row-1 & row+1) | row.
To test the idea, I wrote a quick a command line program. It first outputs the rows of the station using ASCII graphics:
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then again as each row would appear for collision testing:
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The test can be found in the source in subdirectory quadtest. The results looked good, so I dropped it in. We now get a collision in the shadows:
but not in empty spaces outside the image.
I also changed it so that flying into the station will destroy the station as well as the ship.
ROMs
draconian_20140508.bin
draconian_20140508_test.bin
Source
Draconian_20140508.zip