Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Stock-Based Compensation

Schedule of stock option activity

				Weighted-
		Weighted-		Average
	Number of	Average		Remaining
	Shares in	Exercise		Contractual
	(in thousands)	Price		Life (in years)
Options outstanding as of December 31, 2018	21,458	$	1.61
Granted	9,294	$	2.54
Exercised	(88)	$	1.26
Cancelled/forfeited	(6,446)	$	2.48
Options outstanding as of December 31, 2019	24,218		2.16	6.64
Granted	469	$	0.54
Exercised	(201)	$	0.53
Cancelled/forfeited	(8,711)	$	1.95
Options outstanding as of December 31, 2020	15,775			6.51
Options vested and expected to vest as of December 31, 2020	15,775	$	2.27
Options exercisable as of December 31, 2020	12,222	$	2.19	6.10

Schedule of assumptions of Black-Scholes option pricing model

	For the year ended December 31,
	2020				2019				2018
Expected term of options (in years)			6.5				6.5				6.5
Expected volatility rate	66.50	-	67.41	%	64.49	-	67.16	%	63.52	-	66.95	%
Risk-free interest rate	0.41	-	1.80	%	1.60	-	2.64	%	2.45	-	3.08	%
Expected dividend yield			0	%			0	%			0	%

Schedule of employee stock-based compensation expense

	December 31,
	2020		2019		2018
Cost of sales	$	67	$	153		—
Sales and marketing		1,908		3,001	$	1,685
Research and development		1,478		1,600		1,364
General and administrative		3,801		3,298		3,326
Total stock-based compensation	$	7,254	$	8,052	$	6,375