"Fire" in the Android Jetboy Example App

I'm testing the "Jetboy" example Android code in an emulator. It says "Use your fire button..开发者_运维百科.". Where is that? I've clicked all the buttons on my mouse, and hit about all the buttons on my keyboard, and I get nothing.

I was hoping that the following link would help, but I don't see my particular need in it: http://developer.android.com/guide/developing/devices/emulator.html

Thanks for your help!

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You can find the relevant code inside JetBoyView.java, check the processKeyEvent() method.
Fire is the DPAD center, thats usually pressing the trackball/-pad on a device. On the emulator it's this button: