Note 7 - Stockholders' Equity - Warrant Activity (Details) - $ / shares	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Balance, shares (in shares)		340,689
Balance, exercise price (in dollars per share)		$ 19.40
Balance, term (Year)	4 years 2 months 26 days	4 years 2 months 26 days	1 year 10 months 24 days
Warrants granted, shares (in shares)		1,071,429
Warrants expired (in shares)		(13,840)
Warrants exercised (in shares)		(158,731)
Exercisable, shares (in shares)	1,239,547	1,239,547
Balance, exercise price (in dollars per share)	$ 3.80	$ 3.80
Pre-funded Warrant [Member]
Warrants granted, shares (in shares)		946,429
Warrants exercised (in shares)	(946,429)	(946,429)