TABLE A1.

Measurement items.

Construct	Measurement items	References	Factor loadings	t-value
Reward	When playing Stackopolis	Sen et al., 2008; O’Brien, 2010; Kankanhalli et al., 2012
	(1) Awards increases my involvement in the game		0.94	25.40
	(2) I try to get more points as a reward for my activities.		0.93	77.29
	(3) I try to have a higher status as a reward for my activities.		0.94	84.83
	(4) I try to get more badges or loots as a reward for my activities.		0.82	101.88
Competition	When playing Stackopolis	Sheldon et al., 2001; Jang et al., 2009
	(1) I am facing intense competition.		0.84	30.11
	(2) Activities of other participants are threats to me		0.85	31.93
	(3) Competition among participants is fierce.		0.85	28.67
	(4) Competition increases my participation in the game		0.83	50.14
Absorption	When playing Stackopolis	Seaborn and Fels, 2015
	(1) I forget everything else around me.		0.88	46.82
	(2) Time flies.		0.87	41.42
	(3) I am immersed.		0.90	52.07
	(4) It is difficult to detach myself from the website.		0.89	43.52
Autonomy (AUT)	When playing Stackopolis	Sheldon et al., 2001; Jang et al., 2009
	(1) I feel free to decide what to do for myself.		0.85	24.60
	(2) I feel that my choices are based on my true interests and values.		0.85	23.15
	(3) I feel free to do things on my own way.		0.90	42.12
Enjoyment (ENJ)	Stackopolis is	Kim et al., 2013
	(1) interesting.		0.89	51.03
	(2) exciting.		0.93	97.29
	(3) fun.		0.82	35.28
Online Purchase intention	After the game,	Huang et al., 2017
	(1) I bought goods or VIP services on the website.		0.87	36.42
	(2) I intend to pay for some goods or VIP services.		0.90	57.18
	(3) I am able to buy goods or VIP services with the acquired red packet.		0.81	31.54
	(4) I will recommend others to buy goods or VIP services.		0.67	12.33