Note 7 - Shareholders' Equity - Stock Option Activity (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Balance, number of shares (in shares)	1,786,891
Balance, weighted average exercise price (in dollars per share)	$ 2.04
Balance, weighted average remaining contractual life (Year)	7 years 266 days	7 years 273 days
Balance, aggregate intrinsic value	$ 2,789,370	$ 330,831
Granted, number of shares (in shares)	75,000
Granted, weighted average exercise price (in dollars per share)	$ 3.17
Exercised, number of shares (in shares)	(6,963)
Exercised, weighted average exercise price (in dollars per share)	$ 5.15
Forfeited, number of shares (in shares)	(32,450)
Forfeited, weighted average exercise price (in dollars per share)	$ 1.02
Expired, number of shares (in shares)	(10,250)
Expired, weighted average exercise price (in dollars per share)	$ 2.91
Balance, number of shares (in shares)	1,812,228	1,786,891
Balance, weighted average exercise price (in dollars per share)	$ 2.09	$ 2.04
Vested and expected to vest, number of shares (in shares)	1,637,437
Vested and expected to vest, weighted average exercise price (in dollars per share)	$ 2.14
Vested and expected to vest, weighted average remaining contractual life (Year)	7 years 229 days
Vested and expected to vest, aggregate intrinsic value	$ 2,468,576
Exercisable, number of shares (in shares)	800,338
Exercisable, weighted average exercise price (in dollars per share)	$ 2.76
Exercisable, weighted average remaining contractual life (Year)	6 years 219 days
Exercisable, aggregate intrinsic value	$ 909,183