The Company has 10 million shares of undesignated preferred stock authorized but not issued with rights and preferences determined by the Company’s Board of Directors at the time of issuance of such shares. As of June 30, 2021 and December 31, 2020, there were no shares of preferred stock issued and outstanding.

The Company has two classes of authorized common stock, Class A common stock and Class B common stock. Holders of Class A common stock are entitled to one vote for each share of Class A common stock held on all matters submitted to a vote of stockholders and holders of Class B common stock are entitled to ten votes for each share of Class B common stock held on all matters submitted to a vote of stockholders. Except with respect to voting, the rights of the holders of Class A and Class B common stock are identical. Shares of Class B common stock are voluntarily convertible into shares of Class A common stock at the option of the holder and are generally automatically converted into shares of the Company's Class A common stock upon sale or transfer. Shares issued in connection with exercises of stock options, vesting of restricted stock units, or shares purchased under the employee stock purchase plan are generally automatically converted into shares of the Company’s Class A common stock.

On March 2, 2021, the Company entered into an Equity Distribution Agreement with Morgan Stanley & Co. LLC, Citigroup Global Markets Inc. and Evercore Group L.L.C., as its sales agents, pursuant to which the Company could offer and sell from time-to-time shares of its Class A common stock for aggregate gross proceeds of up to $1,000.0 million. In March 2021, the Company sold approximately 2.6 million shares of Class A common stock at an average selling price of $379.26 per share, for aggregate gross proceeds of $1,000.0 million and incurred issuance costs of $10.4 million.

As of June 30, 2021, the Company had reserved shares of common stock for issuance as follows (in thousands):

	As of June 30, 2021
Common stock awards granted under equity incentive plans		10,611
Common stock awards available for issuance under the 2017 Employee Stock Purchase Plan⁽¹⁾		5,089
Common stock awards available for issuance under the 2017 Equity Incentive Plan		27,698
Total reserved shares of common stock		43,398

⁽¹⁾ The Company has not issued any common stock pursuant to the 2017 Employee Stock Purchase Plan.

The Company has two equity incentive plans, the 2008 Equity Incentive Plan (the “2008 Plan”) and the 2017 Equity Incentive Plan (the “2017 Plan”). The 2017 Plan became effective September 2017 in connection with the Company’s initial public offering (“IPO”). No additional equity grants have been made pursuant to the 2008 Plan subsequent to the IPO. The 2017 Plan provides for the grant of incentive stock options to the Company’s employees and for the grant of non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards, performance cash awards, and other forms of equity compensation to the Company’s employees, directors and consultants.

Restricted stock units granted under the 2017 Plan are subject to continuous service. Stock options granted under the 2017 Plan generally are granted at a price per share equivalent to the fair market value on the date of grant. Recipients of option grants who possess more than 10% of the combined voting power of the Company are subject to certain limitations, and incentive stock options granted to such recipients are at a price per share no less than 110% of the fair market value on the date of grant.

The following table summarizes the Company’s restricted stock unit activities for the six months ended June 30, 2021 (in thousands, except per share data):

	Number of Shares			Weighted-Average Grant Date Fair Value per Share
Balance as of December 31, 2020		4,355		$	92.91
Awarded		306			353.72
Released		(806	)		74.62
Forfeited		(188	)		113.42
Balance as of June 30, 2021		3,667		$	117.65

As of June 30, 2021, the Company had $352.8 million of unrecognized stock-based compensation expense related to unvested restricted stock units that is expected to be recognized over a weighted-average period of approximately 2.04 years.

The following table summarizes the Company’s stock option activities for the six months ended June 30, 2021 (in thousands, except years and per share data):

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Balance as of December 31, 2020		8,733		$	26.19		5.7
Granted		67			357.60		—
Exercised		(1,852	)		5.55		—
Forfeited and expired		(4	)		7.56		—
Balance as of June 30, 2021		6,944		$	34.89		5.7	$	2,946,586

Options exercisable as of June 30, 2021		5,108		$	10.77		4.9	$	2,290,669

As of June 30, 2021, the Company had $47.6 million of unrecognized stock-based compensation expense related to unvested stock options that is expected to be recognized over a weighted-average period of approximately 1.86 years.

The Company measures the cost of employee services received in exchange for an equity award based on the grant date fair value of the award. Generally, stock options granted to employees under the 2008 Plan vest 25% after one year and then 1/48th monthly thereafter and have a term of ten years. Stock options granted to employees under the 2017 Plan generally vest over one to four years and have a term of ten years. Restricted stock units generally vest over 4 years. For the three and six months ended June 30, 2021 and 2020, the amount of stock-based compensation capitalized as part of internal-use software was not material.

The following table shows the total stock-based compensation expense for the three and six months ended June 30, 2021 and 2020 (in thousands):

	Three Months Ended				Six Months Ended
	June 30, 2021		June 30, 2020		June 30, 2021		June 30, 2020
Cost of platform revenue	$	167	$	232	$	365	$	443
Cost of player revenue		315		310		730		648
Research and development		18,577		13,348		35,131		26,603
Sales and marketing		14,275		9,615		27,638		19,672
General and administrative		9,212		6,531		19,219		13,075
Total stock-based compensation	$	42,546	$	30,036	$	83,083	$	60,441