Note 7 - Shareholders' Equity - Stock Option Activity (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Balance, number of shares (in shares) | shares	1,544,826
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 2.74
Balance, weighted average remaining contractual life (Year)	8 years 10 days	7 years 171 days
Balance, aggregate intrinsic value | $	$ 214,529	$ 46,582
Granted, number of shares (in shares) | shares	574,900
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 1.03
Exercised, number of shares (in shares) | shares	(25,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 1.35
Forfeited, number of shares (in shares) | shares	(109,656)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 1.72
Expired, number of shares (in shares) | shares	(200,367)
Expired, weighted average exercise price (in dollars per share) | $ / shares	$ 4.82
Balance, number of shares (in shares) | shares	1,784,703	1,544,826
Balance, weighted average exercise price (in dollars per share) | $ / shares	$ 2.07	$ 2.74
Vested and expected to vest, number of shares (in shares) | shares	1,548,348
Vested and expected to vest, weighted average exercise price (in dollars per share) | $ / shares	$ 2.14
Vested and expected to vest, weighted average remaining contractual life (Year)	7 years 328 days
Vested and expected to vest, aggregate intrinsic value | $	$ 172,230
Exercisable, number of shares (in shares) | shares	568,073
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 3.35
Exercisable, weighted average remaining contractual life (Year)	6 years 102 days
Exercisable, aggregate intrinsic value | $	$ 6,601