A Walker is an assistive mobility device that accommodates even terrains and staircases as a vehicle of physical exercise and mental security. It is designed for seniors who are generally active but need occasional assistance and balance control. It can be used outdoor as a walking aid and on stairs as a walker-cane hybrid to provide firm support. Four aspects of aging are the major concerns of A Walker: mental security in seniors’ product environment, independence, safety, and social connectivity. Four corresponding components - telescoping legs, scissors crossbars, fold-up seat pads, and wheels with pressure brakes are designed to solve each problem stated above. In comparison with existing walkers in the market, A Walker bridges seniors’ mobility gap between indoor and outdoor space, making the impossible possible. Climbing stairs is no longer an intimidating challenge but a daily exercise. Only by building stronger bodies and more confident minds can seniors live a healthier life through the process of aging.