Note 11 - Stockholders' Equity - Option Activity for Stock Option Plans (Details) - USD ($)		12 Months Ended
	Jun. 04, 2020	Dec. 31, 2020	Dec. 31, 2019
Outstanding, options (in shares)		291,807
Outstanding, weighted average exercise price, options (in dollars per share)		$ 13.96
Outstanding, weighted average remaining contractual life, options (Year)		8 years 255 days	8 years 109 days
Outstanding, aggregate intrinsic value, options			$ 280,000
Granted, options (in shares)	565,500	615,500
Granted, weighted average exercise price, options (in dollars per share)	$ 5.94	$ 5.92
Forfeited/cancelled, options (in shares)		(17,671)
Forfeited, weighted average exercise price, options (in dollars per share)		$ 5.63
Forfeited/cancelled, aggregate intrinsic value, options		$ 1,840
Outstanding, options (in shares)		889,636	291,807
Outstanding, weighted average exercise price, options (in dollars per share)		$ 8.57	$ 13.96
Vested and expected to vest, options (in shares)		598,092
Vested and expected to vest, weighted average exercise price, options (in dollars per share)		$ 9.72
Vested and expected to vest, weighted average remaining contractual life, options (Year)		8 years 182 days
Vested and expected to vest, aggregate intrinsic value, options
Exercisable, options (in shares)		230,836
Exercisable, weighted average exercise price, options (in dollars per share)		$ 15.21
Exercisable, weighted average remaining contractual life, options (Year)		7 years 182 days
Exercisable, aggregate intrinsic value, options