The Company maintains a stock-based compensation plan, the 2011 Incentive Compensation Plan, as amended, (the “2011 Plan”), to attract, motivate, retain and reward employees, directors and consultants by providing its Board or a committee of the Board the discretion to award equity incentives to these persons.

On June 6, 2011, the Company’s stockholders approved the 2011 Plan, which is administered by the Compensation Committee of the Board. The 2011 Plan provides that stock options, stock units, restricted shares, and stock appreciation rights may be granted to executive officers, directors, consultants, and other key employees. The Company reserved 400,000 shares of common stock under the 2011 Plan, plus 459,956 shares of common stock that remained available for delivery under the 2007 Plan and the 2010 Plan as of June 6, 2011. In aggregate, as of June 6, 2011, 859,956 shares were available for future grant under the 2011 Plan, including shares rolled over from the 2007 Plan and the 2010 Plan. Subsequent to June 6, 2011 through December 31, 2021, the number of shares of common stock authorized for issuance under the 2011 Plan has been increased by an aggregate of 4,400,000 shares.

The following is a summary of stock option activity for the year ended December 31, 2021:

	Number Outstanding			Average Exercise Price per Share		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Balance as of December 31, 2020		550,769		$	5.56	4.88		$	1,875,719
Granted		—			—				—
Cancelled or Expired		(6,142	)		21.46				—
Exercised		(29,934	)		10.00				—
Balance as of December 31, 2021		514,693		$	5.11		4.11	$	11,850,930
Vested or expected to vest as of December 31, 2021		514,693		$	5.11		4.11	$	11,850,930
Exercisable as of December 31, 2021		514,693		$	5.11		4.11	$	11,850,930

The aggregate intrinsic value in the table above represents the difference between the fair value of the Company’s common stock as of December 31, 2021 and the exercise price of in-the-money stock options multiplied by the number of such stock options.

The following table summarizes information about stock options outstanding as of December 31, 2021:

	Stock Options Outstanding						Stock Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (Years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$4.36 - $7.20		452,510		4.37	$	4.41		452,510	$	4.41
$7.50 - $11.25		61,317		2.23		10.19		61,317		10.19
$11.30 - $16.95		500		2.25		11.30		500		11.30
$19.70 - $29.55		366		0.36		19.70		366		19.70
$4.36 - $29.55		514,693		4.11	$	5.11		514,693	$	5.11

As of December 31, 2021, there was no unrecognized stock-based compensation expense related to stock options.

The following is a summary of RSU activity for the year ended December 31, 2021:

	Number Outstanding			Weighted Average Fair Value
Unvested as of December 31, 2020		682,563		$	4.34
Granted		288,368			14.64
Vested		(395,242	)		5.76
Forfeited		(89,960	)		4.92
Unvested as of December 31, 2021		485,729		$	9.19
RSUs vested but not released		296,477		$	5.31

The fair value of the Company’s RSUs is calculated based upon the fair market value of the Company’s common stock at the date of grant. As of December 31, 2021, there was $3.6 million of unrecognized compensation cost related to unvested RSUs granted, which is expected to be recognized over a weighted average period of 2.9 years.

The Company granted 200,000 PSUs to a certain key employee during the year ended December 31, 2020, with a grant date fair value of $6.38 per share. The PSUs are subject to the attainment of performance goals established by the Company’s Compensation Committee, the periods during which performance is to be measured, and other limitations and conditions. Performance goals are based on pre-established objectives that specify the manner of determining the number of PSUs that will vest if performance goals are attained. If the employee terminates employment, the non-vested portion of the PSUs will not vest and all rights to the non-vested portion will terminate.

The following is a summary of PSU activity for the year ended December 31, 2021:

	Number Outstanding
Unvested as of December 31, 2020		200,000
Granted		—
Vested		(23,500	)
Forfeited		(1,500	)
Unvested as of December 31, 2021		175,000

As of December 31, 2021, there was $1.1 million of unrecognized compensation cost related to unvested PSUs, which is expected to be recognized over a period of 1.0 year. No tax benefit was realized from PSUs for the year ended December 31, 2021.

The following table summarizes stock-based compensation expense related to stock options, RSUs, and PSUs included in the consolidated statements of comprehensive income (loss) for the years ended December 31, 2021 and 2020 (in thousands):

	Year Ended December 31,
	2021		2020
Cost of revenue	$	183	$	160
Research and development		486		685
Selling and marketing		545		480
General and administrative		1,392		1,702
Total	$	2,606	$	3,027

During the years ended December 31, 2021 and 2020, the Company repurchased 82,351 and 171,641 shares, respectively, of common stock surrendered to the Company to satisfy tax withholding obligations in connection with the vesting of RSUs issued to employees.