For unlimited shurikens, set the number of shurikens on the Options screen
to 0 and wait about 20 seconds. The zero will turn into an infinity symbol,
giving you an unlimited number of shurikens.
In round 4-2, there are many power-Ups hidden that are revealed only by
shooting them. On the first platform, jump and shoot and you'll reveal a 2-Up
on the platform across your position. Get it, die, and repeat! There's another
2-Up on level 3-2. Go to the second elevator and locate the crates that are
in the middle of the screen (on the second level). Then shoot the
bottom-Left crate until the 2-Up appears.
Finish any level with enough shurikens to equal 11 times the number of
lives remaining, and you will receive 30,000 bonus points (i.e., if you have
7 lives Left, finish the round with exactly 77 shurikens).
