Note 2 - Summary of Significant Accounting Policies - Calculation of Weighted Average Shares Used to Calculate Basic and Diluted Loss Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Weighted average shares outstanding (in shares)	8,831,517	2,774,296	5,803,010	2,774,237
Effect of potentially dilutive common shares from Senior Secured Promissory Note Warrants and the May 2021 Warrants (in shares)	152,681	0	76,341	0
Weighted average shares used in calculating diluted loss per share (in shares)	8,984,198	2,774,296	5,879,351	2,774,237