A seat assembly for task-oriented seating comprises a seat support and a seat coupled to the seat support. The seat is movable under load, such as from the user's weight and movements, relative to the seat support. The seat has a cushion molded over a supporting armature with multiple bias elements. The seat and seat support are configured to deflect by predetermined amounts at defined locations over an extent of the seat assembly. In this way, the seat assembly provides for a range of comfortable and effective positions for users engaged in different active motions and having different preferences and sizes.