Reactoid

Reactoid is an original arcade game in which you try to deflect particles that fire out of the four sides of the reactor, using a small, diagonal paddle that you can flip as the deflector. You have to deflect these particles into the squares occupying the playfield; and you can't deflect into one more than once. You also can not leave a particle travel the width or height of a screen, either... even if multiple ones are flying around in the later levels. A very addictive game... the only thing I have seen close to it is Dave Edson's Tube Frenzy.