Note 4 - Stock-based Compensation - Nonvested Option Awards Activity (Details) - $ / shares	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Nonvested, Shares, Balance (in shares)	29,000	41,000	148,500		148,500
Nonvested, weighted average grant date fair value (in dollars per share)	$ 0.16	$ 0.17	$ 0.20		$ 0.20
Granted, shares (in shares)	0	3,000		3,000	3,000	163,000
Granted, weighted average grant date fair value (in dollars per share)		$ 0.11			$ 0.11
Vested, shares (in shares)	(1,500)	(12,500)	(107,500)
Vested, weighted average grant date fair value (in dollars per share)	$ 0.12	$ 0.17	$ 0.21
Forfeited, shares (in shares)		(2,500)
Forfeited, weighted average grant date fair value (in dollars per share)		$ 0.21
Nonvested, shares (in shares)	27,500	29,000	41,000		27,500
Nonvested, weighted average grant date fair value (in dollars per share)	$ 0.16	$ 0.16	$ 0.17		$ 0.16