Note 6 - Stock-based Compensation - Nonvested Option Awards Activity (Details) - $ / shares	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Nonvested, shares (in shares)	380,000	235,000	18,500	23,500	235,000	23,500
Options granted, shares (in shares)	127,500	145,000	10,000	0	272,500	10,000
Vested, shares (in shares)	(25,000)	0	(15,500)	(5,000)
Forfeited, shares (in shares)	0	0	0	0
Nonvested, shares (in shares)	482,500	380,000	13,000	18,500	482,500	13,000
Nonvested, weighted average grant date fair value (in dollars per share)	$ 0.94	$ 0.36	$ 0.15	$ 0.17	$ 0.36	$ 0.17
Granted, weighted average grant date fair value (in dollars per share)	1.19	1.22	0.08	0
Vested, weighted average grant date fair value (in dollars per share)	1.01	0	0.16	0.21
Forfeited, weighted average grant date fair value (in dollars per share)	0	0	0	0
Nonvested, weighted average grant date fair value (in dollars per share)	$ 0.94	$ 0.94	$ 0.09	$ 0.15	$ 0.94	$ 0.09