Note 4 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Notes Tables

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three Months Ended	Three Months Ended			Six Months Ended	Six Months Ended
	June 30, 2019	June 30, 2018			June 30, 2019	June 30, 2018
Risk-free interest rate	2.31%	2.71%	-	2.92%	2.31%	2.65%	-	2.92%
Dividend yield	0%	0%			0%	0%
Expected term (in years)	5	5			5	5
Expected volatility	57.9%	49.5%	-	51.3%	57.9%	49.0%	-	51.3%

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Options outstanding
				Weighted average		Weighted average	Aggregate
				exercise price		remaining	intrinsic
Incentive Options	Shares			per share		contractual term	value
Outstanding at January 1, 2019		1,376,500		$	0.23
Options granted		-			-
Options exercised		-			-
Options expired		(4,500	)		0.13
Options forfeited		-			-
Outstanding at March 31, 2019		1,372,000		$	0.23
Options granted		3,000			0.21
Options exercised		(10,000	)		0.10
Options expired		(11,000	)		0.08
Options forfeited		(2,500	)		0.46
Outstanding at June 30, 2019		1,351,500		$	0.23	4 years, 4 months	$	33,783
Exercisable at June 30, 2019		1,322,500		$	0.23	4 years, 3 months	$	33,783

Schedule of Nonvested Share Activity [Table Text Block]

	Nonvested
				Weighted average
				grant date
	Shares			fair value
Nonvested at January 1, 2019		148,500		$	0.20
Granted		-			-
Vested		(107,500	)		0.21
Forfeited		-			-
Nonvested at March 31, 2019		41,000		$	0.17
Granted		3,000			0.11
Vested		(12,500	)		0.17
Forfeited		(2,500	)		0.21
Nonvested at June 30, 2019		29,000		$	0.16