To be able to freely view the credits, you need to finish Stage 60. You can then access the "Credits" option from the title screen.
Rapid Fire Mode
Rapid Fire Mode allows you to fire normal shots at an increased rate; to use this once unlocked, you need to hold the stylus on the Touch Screen instead of tapping and releasing as normal. To unlock this mode, you need to finish Stage 60. (Note: Attack tanks will not be able to fire charged shots with this active.)
By meeting certain conditions within the game, you will earn medals, displayed in the lower-left corner of the screen as they are earned.
Unlockable: --- How to Unlock:
Bronze Medal --- Finish Stage 60
Diamond Medal --- Finish all 90 stages with Perfect Clears with both tank types
Gold Medal --- Finish Stage 90
Platinum Medal --- Finish all 90 stages with both tank types
Silver Medal --- Finish Stages 1 - 60 with both tanks
The "Extra" Mode is unlocked after finishing all 90 stages of the game. The option can be then be accessed from the title screen.
In addition to the normal 60 stages initially given to you, there are 30 "bonus" stages you can play that provide additional levels of challenge. To be able to access these, you must finish the first 60 stages with both the Attack and Defense Tanks.