Nintendo Co. is getting more aggressive in the portable video game market, announcing a $20 price cut Tuesday for its newest handheld system. The Nintendo DS is being reduced to $130 from $150. The cut is effective Sunday, a day before the release of the anticipated title "Nintendogs," an interactive puppy simulator that lets owners train and play with a virtual pet. The dogs respond to owners through the built-in microphone and react to praise via the handheld"s touch screen.