On March 12, 2019, the Company entered into an Equity Distribution Agreement with Citigroup Global Markets Inc., as its sales agent, pursuant to which the Company could issue and sell from time-to-time up to $100.0 million maximum aggregate offering price of the Company’s Class A common stock. In March 2019, the Company received gross proceeds of $100.0 million from sales of approximately 1.4 million shares at an average selling price of $72.00 per share and incurred issuance costs of $2.0 million. As of March 31, 2019, the Company had sold all available shares of Class A common stock under this agreement.

On May 16, 2019, the Company entered into an Equity Distribution Agreement with Morgan Stanley & Co. LLC, as its sales agent, pursuant to which the Company could issue and sell up to 1.0 million shares of the Company’s Class A common stock. As of June 30, 2019, the Company received gross proceeds of $82.9 million from the sale of these 1.0 million shares at an average selling price of $82.90 per share and incurred issuance costs of $1.6 million.

The Company is authorized to issue 10 million shares of undesignated preferred stock with rights and preferences determined by the Company’s Board of Directors at the time of issuance.

As of June 30, 2019 and December 31, 2018, 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. All shares of common stock outstanding immediately prior to the initial public offering (“IPO”), including shares of common stock issued upon the conversion of the convertible preferred stock, were converted into an equivalent number of shares of Class B common stock. All common stock, stock options, and restricted stock units issued at the time of, and subsequent to, the IPO are exercised or vested into shares of Class A common stock.

The Company has reserved the following shares of common stock for future issuances (in thousands):

The 2008 Equity Incentive Plan (the “2008 Plan”) became effective in February 2008. The 2008 Plan allowed for the grant of incentive stock options to employees and non-statutory stock options and restricted stock awards to employees, directors and consultants. Subject to certain limitations, options granted under the 2008 Plan were granted at a price per share equivalent to the fair market value on the date of grant and generally vest over four years and have a term of 10 years. Outstanding stock options granted under the 2008 Plan, prior to the Company’s IPO, are exercisable for Class B common stock. Following the Company’s IPO, no further equity awards could be made pursuant to the 2008 Plan.

The 2017 Equity Incentive Plan (the “2017 Plan”) became effective in September 2017. The 2017 Plan provides for the grant of incentive stock options to employees and for the grant of non-statutory stock options and restricted stock awards, as well as other forms of equity compensation to employees, directors and consultants. Stock options and restricted stock units under the 2017 Plan are generally expensed over four years and have a term of 10 years. Only shares of Class A common stock are issued pursuant to equity awards granted under the 2017 Plan.

The Company measures the cost of awards granted under equity incentive plans based on the grant date fair value. The Company uses the straight-line method for expense recognition and recognizes forfeitures as they occur.

The following table shows total stock-based compensation expense for the three and six months ended June 30, 2019 and 2018 (in thousands):

	Three Months Ended				Six Months Ended
	June 30, 2019		June 30, 2018		June 30, 2019		June 30, 2018
Cost of platform revenue	$	59	$	19	$	118	$	38
Cost of player revenue		246		67		489		111
Research and development		9,258		2,801		17,790		5,097
Sales and marketing		4,974		1,286		10,140		2,396
General and administrative		4,134		1,136		7,998		2,096
Total stock-based compensation	$	18,671	$	5,309	$	36,535	$	9,738

The summary of the Company’s stock option activity is as follows (in thousands, except price per share data):

	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)		Weighted Average Grant Date Fair Value Per Share		Aggregate Intrinsic Value
Balance, December 31, 2018 - outstanding		16,371		$	8.59				—
Granted		26			80.25		—	$	28.95
Exercised		(3,625	)		5.37		—		—
Forfeited and expired		(339	)		8.39		—		—
Balance, June 30, 2019 - outstanding		12,433		$	9.68		6.5		—	$	1,005,879

Options exercisable at June 30, 2019		6,860		$	5.12		5.2		—	$	586,269

The intrinsic value for options exercised during the three months ended June 30, 2019 and 2018, was $135.8 million and $140.8 million, respectively, and during the six months ended June 30, 2019 and 2018 was $245.5 million and $197.0 million, respectively. Intrinsic value represents the difference between the fair values of the Company’s common stock and the exercise prices on the date of grant. As of June 30, 2019, the Company had $29.8 million of unrecognized stock compensation expense related to unvested stock options that is expected to be recognized over a weighted-average period of approximately 1.9 years.

The fair value of options granted under the equity incentive plans is estimated on the grant date using the Black-Scholes option-valuation model. The assumptions used in the Black-Scholes model are as follows:

	Three Months Ended					Six Months Ended
	June 30, 2019			June 30, 2018		June 30, 2019			June 30, 2018
Dividend rate		—			—		—			—
Expected term (in years)	5.0 - 5.27			5.3 - 6.1		5.0 - 5.27			5.3 - 6.1
Risk-free interest rate	1.83 - 2.31%			2.61 - 2.88%		1.83 - 2.56%			2.32 - 2.88%
Expected volatility		36	%	38 - 39%			36	%	38 - 40%

Pursuant to the 2017 Plan, the Company grants restricted stock units to employees. The fair value of restricted stock units is based on the Company’s closing stock price on the date of grant. The summary of the Company’s restricted stock unit activity is as follows (in thousands, except price per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Balance, December 31, 2018 - outstanding		3,686		$	48.50
Awarded		1,081			57.36
Released		(381	)		46.16
Forfeited		(224	)		53.46
Balance, June 30, 2019 - outstanding		4,162		$	50.75

The unrecognized compensation cost related to restricted stock units as of June 30, 2019 was $189.1 million, which the Company expects to recognize over 3.0 years. The intrinsic value of restricted stock units that vested during the three months ended June 30, 2019 and 2018 was $19.4 million and $0.3 million, respectively, and during the six months ended June 30, 2019 and 2018 was $30.8 million and $0.3 million, respectively, which represented the fair value of the Company’s common stock underlying the restricted stock units on their vesting date.