Note 9 - Share Based Payments - Stock Option Activity (Details) - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Shares under option (in shares)		2,461,000	2,220,000
Shares under option, Weighted average exercise price (in dollars per share)		$ 0.15	$ 0.48
Options granted, shares (in shares)		250,000	2,557,000
Options granted, Weighted average exercise price (in dollars per share)		$ 0.49	$ 0.10
Options exercised, shares (in shares)		(90,000)
Options exercised, Weighted average exercise price (in dollars per share)		$ 0.10
Options cancelled and expired, shares (in shares)		(49,000)	(2,316,000)
Options cancelled and expired, Weighted average exercise price (in dollars per share)		$ (0.37)	$ (0.41)
Shares under option, Weighted average remaining contractual life (Year)		7 years 292 days	8 years 240 days
Shares under option, shares (in shares)		2,572,000	2,461,000
Shares under option, Weighted average exercise price (in dollars per share)		$ 0.18	$ 0.15
Shares under option, Aggregate intrinsic value	[1]	$ 1,700

[1] Aggregate intrinsic value includes only those options with intrinsic value (options where the exercise price is below the market price).