An extension for a dock including a platform having a one or more sleeves in which accessory members can be inserted and securedlocked. The invention matches the acoustic input to a number of signal models, one per source class, and produces a goodness-of-match number for each signal model. A target region controlling unit ) moves the target region, in response to a change of the viewpoint position or the sight line direction, based on the viewpoint position and sight line direction after the change. A payline display displays scored events. The outer tub is positioned in the casing to be tilted forward at a predetermined angle for containing washing water.