Abstract: A pen-type computer input device operates in the same fashion as a mouse with the added advantage that the device has the features of a ball point pen having a narrow tip, with a small diameter ballpoint for tracing fine detail. The point may optionally deposit ink on the path traversed. The device has an elongate housing which may be grasped like a pen. A stack of contiguous spheres rotatably mounted within the housing serially transmits motion of the lowermost tip sphere to the uppermost sphere which operates as a mouse ball to provide computer signal input directly related to motion of the pen tip. The device may incorporate a mouse at the top or be adapted for retrofit to an existing mouse.