Note 6 - Shareholders' Equity - Stock Option Activity (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Balance, number of shares (in shares)	1,664,014
Balance, weighted average exercise price (in dollars per share)	$ 2.07
Balance, weighted average remaining contractual life (Year)	6 years 8 months 12 days	6 years 7 months 20 days
Balance, aggregate intrinsic value	$ 385,088	$ 405,223
Granted, number of shares (in shares)	50,000
Granted, weighted average exercise price (in dollars per share)	$ 1.84
Exercised, number of shares (in shares)	(54,167)
Exercised, weighted average exercise price (in dollars per share)	$ 1.20
Forfeited, number of shares (in shares)	(8,125)
Forfeited, weighted average exercise price (in dollars per share)	$ 1.02
Expired, number of shares (in shares)	(26,625)
Expired, weighted average exercise price (in dollars per share)	$ 3.45
Balance, number of shares (in shares)	1,625,097	1,664,014
Balance, weighted average exercise price (in dollars per share)	$ 2.07	$ 2.07
Vested and expected to vest, number of shares (in shares)	1,625,097
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 2.07
Vested and expected to vest, weighted average remaining contractual life (Year)	6 years 8 months 12 days
Vested and expected to vest, aggregate intrinsic value	$ 385,088
Exercisable, number of shares (in shares)	988,838
Exercisable, weighted average exercise price (in dollars per share)	$ 2.38
Exercisable, weighted average remaining contractual life (Year)	6 years 1 month 17 days
Exercisable, aggregate intrinsic value	$ 189,808