Note 3 - Warrants (Details Textual) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Share-Based Payment Arrangement, Expense		$ 513,000	$ 514,000	$ 1,012,000	$ 1,041,000
Equity Classified Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	150,000	150,000		150,000
Warrants and Rights Outstanding, Term (Year)	10 years	10 years		10 years
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 0.60	$ 0.60		$ 0.60
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)	4 years
Class of Warrant or Right, Outstanding (in shares)	796,501	796,501		796,501		646,501
Class of Warrant or Right, Vested and Exercisable (in shares)	420,509	420,509		420,509		400,859
Share-Based Payment Arrangement, Expense		$ 46,000	$ 83,000	$ 92,000	$ 166,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 410,000	$ 410,000		$ 410,000