Note 6 - Warrants - Warrants Outstanding (Details) - $ / shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Balance, outstanding (in shares)	49,023,398	36,765,502
Granted (in shares)	10,669,896	19,604,796
Expired (in shares)	(5,173,209)	(4,016,754)
Expired, price range (in dollars per share)		$ 0.48
Balance, outstanding (in shares)	54,520,085	52,353,544
Minimum [Member]
Balance, outstanding, price range (in dollars per share)	$ 0.13	$ 0.16
Granted, price range (in dollars per share)	0.21	0.20
Expired, price range (in dollars per share)	0.19
Balance, outstanding, price range (in dollars per share)	0.13	0.14
Maximum [Member]
Balance, outstanding, price range (in dollars per share)	0.26	0.27
Granted, price range (in dollars per share)	0.25	0.24
Expired, price range (in dollars per share)	0.21
Balance, outstanding, price range (in dollars per share)	0.26	0.25
Weighted Average [Member]
Balance, outstanding, price range (in dollars per share)
Granted, price range (in dollars per share)
Expired, price range (in dollars per share)
Balance, outstanding, price range (in dollars per share)	$ 47,000