Note 11 - Stockholders' Equity - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Common stock equivalents of convertible promissory notes and accrued interest (in shares)	1,872,843	199,310
Convertible Debt Securities [Member]
Common stock equivalents of convertible promissory notes and accrued interest (in shares)	1,525,751	176,907
Warrant, Other [Member]
Common stock equivalents of convertible promissory notes and accrued interest (in shares)	340,689	14,518
Share-Based Payment Arrangement, Option [Member]
Common stock equivalents of convertible promissory notes and accrued interest (in shares)	6,403	7,885