The object of the game is to kill the other tank before it kills you. Health is displayed by a colored ring around your tank. Green is full health, Yellow is 75% health, Orange is 50% health, and Red is 25% health. You adjust the angle of your shot by holding L and R. Angle is displayed in the upper left of the screen. You can change weapons by pressing Circle. You can move left and right by using the joypad, although you will not be able to climb steep hills. To shoot, hold the X button, and release. Wind direction and strength is displayed in the upper center of your screen, this can affect your shot, so keep it in mind while aiming.

http://forums.qj.net/f-psp-development-forum-11/t-release-pyblast-01-130125.html