11. Bring death to the Alien Mothership and a new rank may fall to you!

Explanation
Killing the HURRY UP ships will always drop a RANK MARKER that you need.

How?
Shoot a HURRY UP ship to complete this secret.

12. When an Alien Mothership has passed eight times a great fortune may be collected!

Explanation
When 8 HURRY UP ships have passed in one level a Moneyship will appear. It won't fire at you and when you destroy it it will drop a large amount of money!

How?
Just survive 8 HURRY UP ships in one level and wait for the Moneyship to appear to complete this secret. It is recommended to have a good weapon (eg. Laserbeam), armour and scooped aliens.

13. While holding two Aliens use the scoop to force the others away for extra points!

Explanation
When you have already collected two aliens in your Scoop, any addition ones that fall into it will be tossed away for 2,500 points each!

How?
Just collect a SCOOP and collect 3+ aliens without one of them dying to complete this secret.

14. Buying rank markers when all is collected will bring you extra points!

Explanation
If you have already got all 6 RANK MARKERS and buy another one in the shop, you'll get 1,000,000 points!

How?
Just buy a RANK MARKER at the shop when you've already got all 6 to complete this secret. This secret unlocks the secret seventh rank marker.

15. A doubler of money when there is no money will give you 30 seconds of time!

Explanation
Collecting the XC icon (MONEY DOUBLER) when you have zero credits will add 30 seconds to the green TIME BAR.

How?
You must collect an XC icon (either in game or in a Memory Station) with $0. Possibly easier earlier on the game before you've collected money! Other than that spend all your money in the shop and try to collect the XC icon!

16. Killing all aliens in one formation before they rest will give you bonus points!

Explanation
Destroying a wave of aliens before they reach their final position will give you a 10,000 point bonus.

How?
Just shoot a wave of aliens on a level while they're flying onto the screen to complete this secret.

17. Killing the Top Alien in a group attack can give you a good score!

Explanation
Sometimes aliens form groups of at least three and cover the top alien. Killing this highest one will give you a 1,000 point bonus.

How?
Just look for a group of aliens moving from the pack to attack you in tandem. Shoot them all (or just the top one if you're a sharpshooter) to complete this secret.

18. Catching the same weapon will bring you more power.

Explanation
Collecting the falling Icon for a weapon you're already using will give you an EXTRA BULLET.

How?
Just collect an icon for a weapon you've already got to complete this secret.

19. A mirror rainbow will add D levels to your savings.

Explanation
Collecting rank markers in reverse order (pink blue green yellow orange red) without collecting more than one of each will add 500 levels to the levels played total in your profile. This only works every 50 levels.

How?
"Hurry Up Ship" can help you out, because they are looting Rank Markers that you don't have. Be sure not to collect ranks from question marks, memory station or shop.

20. Getting maximum Speed, Bullets, Time or Armour will get you more points.

Explanation
Getting the maximum amount of Speed, Bullets, Time, Bulletspeed or Armour will mean you get 25,000 points every time you collect more.

How?
Just collect one of the above icons when you're already maxed out to complete this secret. You can buy missing extras in the shop.

Source: warblade.fandom.com