Note 10 - Shareholders' Equity - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Balance, number of shares (in shares)	1,664,014	1,786,891
Balance, weighted average exercise price (in dollars per share)	$ 2.07	$ 3.10
Balance, weighted average remaining contractual life (Year)	5 years 2 months 1 day	6 years 7 months 20 days	7 years 9 months
Balance, aggregate intrinsic value	$ 43,783	$ 405,223	$ 330,831
Granted, number of shares (in shares)	112,000	195,000
Granted, weighted average exercise price (in dollars per share)	$ 1.57	$ 2.76
Exercised, number of shares (in shares)	(69,631)	(36,130)
Exercised, weighted average exercise price (in dollars per share)	$ 1.16	$ 1.88
Forfeited, number of shares (in shares)	(97,867)	(180,592)
Forfeited, weighted average exercise price (in dollars per share)	$ 1.53	$ 1.95
Expired, number of shares (in shares)	(69,238)	(101,155)
Expired, weighted average exercise price (in dollars per share)	$ 3.21	$ 3.24
Balance, number of shares (in shares)	1,539,278	1,664,014	1,786,891
Balance, weighted average exercise price (in dollars per share)	$ 2.05	$ 2.07	$ 3.10
Vested and expected to vest, number of shares (in shares)	1,539,278
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 2.05
Vested and expected to vest, weighted average remaining contractual life (Year)	5 years 2 months 1 day
Vested and expected to vest, aggregate intrinsic value	$ 43,783
Exercisable, number of shares (in shares)	1,169,731
Exercisable, weighted average exercise price (in dollars per share)	$ 2.22
Exercisable, weighted average remaining contractual life (Year)	4 years 6 months 10 days
Exercisable, aggregate intrinsic value	$ 31,617