Note 6 - Warrants - Warrants Outstanding (Details) - $ / shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Balance, outstanding (in shares)	49,023,398	36,765,502
Granted (in shares)	10,669,896	27,137,048
Expired (in shares)	(11,313,584)	(10,273,722)
Balance, outstanding (in shares)	48,379,710	53,628,828
Minimum [Member]
Balance, outstanding, price range (in dollars per share)	$ 0.13	$ 0.16
Granted, price range (in dollars per share)	0.21	0.2
Expired, price range (in dollars per share)	0.1	0.19
Balance, outstanding, price range (in dollars per share)	0.13	0.14
Maximum [Member]
Balance, outstanding, price range (in dollars per share)	1	1
Granted, price range (in dollars per share)	0.29	0.29
Expired, price range (in dollars per share)	0.48	0.48
Balance, outstanding, price range (in dollars per share)	1	1
Weighted Average [Member]
Balance, outstanding, price range (in dollars per share)	0.26	0.27
Granted, price range (in dollars per share)	0.26	0.23
Expired, price range (in dollars per share)	0.23	0.25
Balance, outstanding, price range (in dollars per share)	$ 0.27	$ 0.26