Note 6 - Stockholders' Equity - Warrants (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Outstanding, number of shares (in shares)	4,268,221
Outstanding, weighted average exercise price (in dollars per share)	$ 2.18
Outstanding, weighted average remaining life (Year)	7 months 6 days	6 months
Outstanding, Intrinsic value	$ 116,549	$ 0
Issued, number of shares (in shares)	0
Issued, weighted average exercise price (in dollars per share)	$ 0
Exercised, number of shares (in shares)	0
Exercised, weighted average exercise price (in dollars per share)	$ 0
Expired or cancelled, number of shares (in shares)	(3,953,649)
Expired or cancelled, weighted average exercise price (in dollars per share)	$ 0
Outstanding and exercisable at June 30, 2023 (in shares)	314,572	4,268,221
Outstanding and exercisable at June 30, 2023 (in dollars per share)	$ 0.50	$ 2.18