Note 7 - Shareholders' Equity - Stock Option Activity (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Balance, number of shares (in shares) | shares	1,786,891
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 2.04
Balance, weighted average remaining contractual life (Year)	7 years 1 month 24 days	7 years 9 months
Balance, aggregate intrinsic value | $	$ 1,220,636	$ 330,831
Granted, number of shares (in shares) | shares	175,000
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 2.88
Exercised, number of shares (in shares) | shares	(36,130)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 1.88
Forfeited, number of shares (in shares) | shares	(74,759)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 1.34
Expired, number of shares (in shares) | shares	(62,750)
Expired, weighted average exercise price (in dollars per share) | $ / shares	$ 2.62
Balance, number of shares (in shares) | shares	1,788,252	1,786,891
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 1.92	$ 2.04
Vested and expected to vest, number of shares (in shares) | shares	1,670,375
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 2.17
Vested and expected to vest, weighted average remaining contractual life (Year)	7 years 21 days
Vested and expected to vest, aggregate intrinsic value | $	$ 1,122,212
Exercisable, number of shares (in shares) | shares	934,877
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 2.58
Exercisable, weighted average remaining contractual life (Year)	6 years 1 month 6 days
Exercisable, aggregate intrinsic value | $	$ 496,868