wow superplay nice clear! im stuck on one of the bosses myself. pretty tough game at times
The secret to the first stages is when you loose a life/power-ups jump back to an early stage and level up.
However on the final stage you cannot do this, so remember to make a note of your level 4 code! Then you can use this and level back up.
I found I lost a bunch of lives on the last level because I was impatient and tried to rush too much! The level is still a bitch though and it is one of the multi-part ones.
Good Luck!