Hint: Extra health:
Go to the shop in level 2, and move to the bottom of the screen. Rapidly fire and walk towards the right side of the screen. Keep firing as the game starts to beep until a red potion appears. Use it to increase your characters health by 200%.
Hint: Defeating the World 1 Boss:
To defeat the log, get the bombs that you like the best and fight from the top of the screen. Fire away, as the logs do not fly that high.
Hint: Defeating the World 5 Boss:
To defeat the blowfish, buy a fireball and race to the warp. When he is biggest, fire once and you will win.