Shoot the bomber as fast as you can before it can complete its mission. But beware, its shields can deflect your missiles.
Use Z to move right, . to move left, and M to fire.
JSZeddy, by Erik Olofsen based on JSSpeccy and Z81 emus.
For programs that don’t auto-run, press R then ENTER.
Also you may need to click on the applet to enable keyboard entry.