Orange Technology, a concept that originated in Taiwan, sets the goal to bring more happiness and promote mental wellness for the elderly. This study adopted a virtual orchid planting game symbolizing Orange Technology for a case study through explorative panel discussion followed by focus group interviews which separately included elderly and middle-aged people. This study aimed to find key factors influencing the development of Orange Technology Game (OTG) by introducing technology acceptance model (TAM) analysis. The results show that providing more recreational experiences (RE) and enhancing game induced self-efficacy (GISE) are two key factors, in which, memory improvement, social contact and self-learning are identified for RE, and perceived enjoyment, emotional stability and knowledge exchange are identified for GISE. Moreover, a hypothesis for seniors' TAM is proposed as that GISE will mediate RE to influence seniors' happiness & mental wellness along three identified dimensions of "mental health care", "social relationships" and "leisure atisfaction". In addition, middle-aged people showed more enthusiasm than elderly people for each dimension, such that Orange Technology game should shed light on these key factors to fulfill the needs of elder care.