6. Common Shares

Warrants

Warrant activity is summarized in the following table:


		Weighted		Weighted
		average		average
	Warrants	exercise price		remaining life
	outstanding	per share		(yrs.)	Intrinsic value
As of December 31, 2017	6,514,625		1.92	1.6		—
As of March 31, 2018	6,514,625	$	1.92	1.4	$	—

Stock-Based Compensation

Under our Stock Option Plan (the “Plan”) and our Long-Term Equity Incentive Plan (the “LTIP”), we may grant options and/or restricted stock units (“RSUs”) or restricted stock awards to our directors, officers, employees and consultants. The combined maximum number of our common shares (“Common Shares”) that may be reserved for issuance under the Plan and the LTIP is a variable number equal to 10% of the issued and outstanding Common Shares on a non-diluted basis at any one time. Options and RSUs under the Plan and LTIP, respectively, are granted from time to time at the discretion of the Board of Directors of the Company (“Board”), with vesting periods and other terms as determined by the Board.

Stock-based compensation expense for the three months ended March 31, 2018 and 2017 is as follows:


	Three Months Ended March 31,
	2018		2017
Stock options	$	146	$	12
Restricted stock units		192		234
	$	338	$	246

As of March 31, 2018, stock options and RSUs had unrecognized compensation expense of $258 and $667, respectively, which is expected to be recognized over a weighted average period of 1.4 and 1.2 years, respectively.

Stock Options

A summary of options under the Plan as of March 31, 2018 is set forth in the following table:


		Weighted average		Weighted average	Aggregate
	Number of	exercise price		remaining	intrinsic
	options	per option		contractual term	value
Outstanding - December 31, 2017	1,144,500	$	0.42	1.15	$	346
Granted	820,000		0.75			8
Outstanding - March 31, 2018	1,964,500	$	0.56	2.58	$	374

Exercisable - March 31, 2018	1,164,912	$	0.50	1.85	$	284

A summary of our unvested stock options as of March 31, 2018 is set forth in the following table:


				Weighted
		Weighted		average
		average		remaining
		grant-date		amortization
	Number of	fair value		period
	options	per option		(Years)
Unvested - December 31, 2017	246,250	$	0.22	0.99
Granted	820,000		0.48
Vested	(266,662)		0.48
Unvested - March 31, 2018	799,588	$	0.40	1.40

No stock options were granted for the three months ended March 31, 2017. The fair value of stock options granted during the three months ended March 31, 2018 to employees, directors and consultants was estimated at the grant date using the Black-Scholes option pricing model using the following assumptions:



	2018
Expected volatility	77.1	%
Risk-free interest rate	2.6	%
Expected life (years)	5
Dividend yield	—
Forfeiture assumption	—	%

Restricted Stock Units

The following table summarizes the RSUs outstanding under the LTIP as of March 31, 2018:


		Weighted average
	Number	grant-date fair
	of units	value per unit
Unvested - December 31, 2017	1,567,907	$	0.85
Cancelled/forfeited	(101,392)		0.98
Vested, net of shares withheld	(127,942)		0.97
Granted	319,000		0.75
Unvested - March 31, 2018	1,657,573	$	0.81

A portion of the RSU awards vest on a fixed future date provided the recipient continues to be affiliated with Vista on that date. Other RSU awards vest subject to certain performance and market criteria, including the accomplishment of certain corporate objectives and the Company’s share price performance. The minimum vesting period for RSUs is one year.

During the three months ended March 31, 2018, the Company withheld shares with an equivalent value to the employee withholding tax obligation which resulted from RSUs that vested in the period. Shares withheld are considered cancelled/forfeited.