We recorded stock-based compensation expense related to grants of employee stock options, restricted stock units (“RSUs”) and performance and market-based awards in our consolidated statements of operations as follows (in millions):

	Three Months Ended March 31,
	2022		2021
Cost of revenue	$	0.7	$	0.6
Research and development		31.0		24.3
Sales and marketing		4.8		3.9
General and administrative		8.5		8.4
Total stock-based compensation expense	$	45.0	$	37.2

The following table shows stock option activity for the three months ended March 31, 2022 (in millions, except weighted-average exercise price and weighted-average contractual term):

	Outstanding Options
						Aggregate		Weighted-
				Weighted-Average		Intrinsic Value of		Average
				Exercise Price		Stock Options		Contractual Term
	Stock Options			(per option)		Outstanding		(in years)
Balance as of December 31, 2021		22.7		$	3.56	$	64.9		5.71
Granted		—			—
Forfeited, expired and cancelled		—			—
Exercised		(0.2	)		3.21
Balance as of March 31, 2022		22.5		$	3.56	$	127.8		5.37

The following table shows a summary of RSU activity for the three months ended March 31, 2022, which includes performance and market-based awards (in millions, except weighted-average grant date fair value):

	Outstanding RSUs
				Weighted-Average		Aggregate
				Grant Date Fair Value		Intrinsic Value of
	Shares			(per share)		Unvested RSUs
Unvested as of December 31, 2021		62.4		$	8.68	$	399.4
Granted		17.6			8.86
Vested		(5.8	)		8.30
Forfeited		(1.5	)		8.50
Unvested as of March 31, 2022		72.7		$	8.76	$	671.7

On March 15, 2022, the Company granted performance-based awards to certain executives and senior management (the “2022 Performance RSUs”) and members of studio management (the “2022 Studio Performance RSUs”). As it relates to the 2022 Performance RSUs, the number of shares earned will range from 0% to 150% of the target number of shares granted, depending on an adjusted operating cash flow metric for the year ended December 31, 2022 relative to pre-established thresholds. Shares earned (if any) based on the level of achievement will vest over a period of four years following the grant date, with 25% vesting on the one year anniversary of the grant date and the remaining quarterly thereafter, subject to continued service by the employees. The target number of shares granted totaled 1.1 million.

As it relates to the 2022 Studio Performance RSUs, the number of shares earned will range from 0% to 100% of the target number of shares granted, depending on bookings and/or profitability metrics for the individual studios during the year ended December 31, 2022 relative to pre-established thresholds. Shares earned (if any) based on the level of achievement will vest over either one or four years following the grant date, depending on the terms of award. All of the 2022 Studio Performance RSUs are subject to continued service by the employees. The target number of shares granted across all of the 2022 Studio Performance RSUs totaled 0.9 million.

In April 2018, a share repurchase program was authorized for up to $200.0 million of our outstanding Class A common stock (the “2018 Share Repurchase Program”). The 2018 Share Repurchase Program remained in effect until April 2022. During the three months ended March 31, 2022, no share repurchases were made under the 2018 Share Repurchase Program. As of March 31, 2022, we had $173.8 million remaining under the 2018 Share Repurchase Program.