Note 6 - Warrants - Warrants Outstanding (Details) - USD ($)		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021
Balance, outstanding (in shares)		36,765,502	32,980,989
Issued (in shares)		27,137,048	7,865,872
Expired (in shares)		(10,273,722)	(2,743,406)
Balance, aggregate intrinsic value	[1]	$ 2,094,000
Exercised (in shares)			(416,667)
Exercised (in dollars per share)			$ 0.14
Balance, outstanding (in shares)		53,628,828	37,686,788
Minimum [Member]
Balance, outstanding, price range (in dollars per share)		$ 0.16	$ 0.16
Granted, price range (in dollars per share)		0.19	0.14
Expired (in dollars per share)		0.19	0.12
Exercised (in dollars per share)
Balance, outstanding, price range (in dollars per share)		0.14	0.12
Maximum [Member]
Balance, outstanding, price range (in dollars per share)		1.00	1.00
Granted, price range (in dollars per share)		0.33	0.27
Expired (in dollars per share)		0.48	0.70
Exercised (in dollars per share)
Balance, outstanding, price range (in dollars per share)		1.00	1.00
Weighted Average [Member]
Balance, outstanding, price range (in dollars per share)		0.27	0.29
Granted, price range (in dollars per share)		0.23	0.20
Expired (in dollars per share)		0.25	0.59
Exercised (in dollars per share)			0.14
Balance, outstanding, price range (in dollars per share)		$ 0.26	$ 0.27

[1] Aggregate intrinsic value based on closing common stock price of $0.27 at September 30, 2022