Note 4 - Stockholders' Equity, Stock Options and Warrants - Summary of Transactions for Stock Options and Warrants (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Warrants, outstanding (in shares)	31,699,885	7,353,376
Warrants, average exercise price (in dollars per share)	$ 1.66	$ 1.99
Warrants, issued (in shares)	21,062,714	29,640,801
Issued, average exercise price, warrants (in dollars per share)	$ 0.70	$ 1.44
Warrants,forfeited (in shares)	0	0
Warrants,expired (in shares)	(108,435)	(25,233)
Expired, average exercise price, warrants (in dollars per share)	$ 16.48	$ 10.00
Warrants,exercised (in shares)		(5,269,059)
Exercised, average exercise price, warrants (in dollars per share)		$ 0.86
Warrants,cancelled (in shares)	(16,325,433)
Cancelled, average exercise price, warrants (in dollars per share)	$ 1.51
Number of Shares Outstanding (in shares)	981,060
Warrants, outstanding (in shares)	36,328,731	31,699,885
Warrants, average exercise price, warrants (in dollars per share)	$ 1.13	$ 1.66
Share-Based Payment Arrangement, Option [Member]
Number of Shares Outstanding (in shares)	1,062,871	1,013,547
Average Exercise Price Outstanding (in dollars per share)	$ 4.83	$ 5.41
Number of Shares Issued (in shares)	31,970	147,230
Average Exercise Price Issued (in dollars per share)	$ 0.42	$ 1.06
Number of Shares Forfeited (in shares)	(40,241)	(92,593)
Average Exercise Price Forfeited (in dollars per share)	$ 0.88	$ 8.64
Number of Shares Expired (in shares)	(73,540)	0
Average Exercise Price Expired (in dollars per share)	$ 10.42	$ 0
Number of Shares Exercised (in shares)		(5,313)
Average Exercise Price Exercised (in dollars per share)		$ 0.74
Number of Shares Cancelled (in shares)	0
Average Exercise Price Cancelled (in dollars per share)	$ 0
Number of Shares Outstanding (in shares)	981,060	1,062,871
Average Exercise Price Outstanding (in dollars per share)	$ 4.58	$ 4.83