Note 10 - Share-based Compensation - Stock Option Activity (Details) - USD ($)		12 Months Ended
	Jan. 29, 2020	Dec. 31, 2021	Dec. 31, 2020
Stock options outstanding, beginning of period (in shares)		1,114,306
Balance, weighted average exercise price, beginning of period (in dollars per share)		$ 5.89
Stock options outstanding, weighted average remaining contractual term (Year)		7 years 7 months 6 days	7 years 6 months
Stock options outstanding, aggregate intrinsic value			$ 177,100
Stock options granted (in shares)	515,036	772,435
Stock options granted, weighted average exercise price (in dollars per share)	$ 5.32	$ 3.56
Stock options exercised (in shares)		(1,580)
Stock options exercised, weighted average exercise price (in dollars per share)		$ 2.49
Stock options forfeited (in shares)		(235,350)
Stock options forfeited, weighted average exercise price (in dollars per share)		$ 4.49
Stock options expired (in shares)		(125)
Stock options expired, weighted average exercise price (in dollars per share)		$ 5.32
Stock options outstanding, end of period (in shares)		1,649,686	1,114,306
Balance, weighted average exercise price, end of period (in dollars per share)		$ 5.00	$ 5.89
Exercisable, December 31, 2021 (in shares)		762,867
Options exercisable, weighted average exercise price (in dollars per share)		$ 6.62
Options exercisable, weighted average remaining contractual term (Year)		6 years
Options vested and expected to vest (in shares)		1,649,686
Options vested and expected to vest, weighted average exercise price (in dollars per share)		$ 5.00
Options vested and expected to vest, weighted average remaining contractual term (Year)		7 years 7 months 6 days