Note 13 - Employee Equity Incentive Plans - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of shares (in shares)	5,275,000	1,225,000
Weighted average exercise price (per share) (in dollars per share)	$ 0.26	$ 0.17
Weighted average remaining contractual term (in years) (Year)	3 years 171 days	4 years 32 days	2 years 226 days
Aggregate intrinsic value	$ 16,675	$ 130,475	$ 83,425
Number of shares, granted (in shares)	570,000	4,650,000
Weighted average exercise price (per share), granted (in dollars per share)	$ 0.28	$ 0.26
Number of shares, exercised (in shares)	(300,000)	(300,000)
Weighted average exercise price (per share), exercised (in dollars per share)	$ 0.21	$ 0.13
Number of shares, forfeited/cancelled/expired (in shares)	(2,975,000)	(300,000)
Weighted average exercise price (per share), forfeited/cancelled/expired (in dollars per share)	$ 0.25	$ 0.14
Number of shares (in shares)	2,570,000	5,275,000	1,225,000
Weighted average exercise price (per share) (in dollars per share)	$ 0.28	$ 0.26	$ 0.17
Vested and exercisable at December 31, 2018 (in shares)	887,500
Vested and exercisable at December 31, 2018 (in dollars per share)	$ 0.25
Vested and exercisable at December 31, 2018 (Year)	2 years 335 days
Vested and exercisable at December 31, 2018	$ 14,425