Note 7 - Shareholders' Equity - Stock Option Activity (Details)	6 Months Ended	12 Months Ended
	Jun. 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 5 months 26 days	7 years 9 months
Balance, aggregate intrinsic value | $	$ 4,987,776	$ 330,831
Granted, number of shares (in shares) | shares	160,000
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 2.89
Exercised, number of shares (in shares) | shares	(24,255)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 2.20
Forfeited, number of shares (in shares) | shares	(43,450)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 1.51
Expired, number of shares (in shares) | shares	(62,200)
Expired, weighted average exercise price (in dollars per share) | $ / shares	$ 2.60
Balance, number of shares (in shares) | shares	1,816,986	1,786,891
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 2.11	$ 2.04
Vested and expected to vest, number of shares (in shares) | shares	1,670,128
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 2.15
Vested and expected to vest, weighted average remaining contractual life (Year)	7 years 4 months 20 days
Vested and expected to vest, aggregate intrinsic value | $	$ 4,527,651
Exercisable, number of shares (in shares) | shares	860,520
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 2.67
Exercisable, weighted average remaining contractual life (Year)	6 years 4 months 9 days
Exercisable, aggregate intrinsic value | $	$ 1,957,927