Note 8 - Stock-based Compensation - Restricted Stock Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Beginning balance, unvested restricted stock units, shares (in shares)	100,005	775,635
Beginning balance, unvested restricted stock units, weighted average grant date fair value (in dollars per share)	$ 1.50	$ 1.47
Forfeited, restricted stock units, shares (in shares)	(5,000)	(70,000)
Forfeited, restricted stock units, weighted average grant date fair value (in dollars per share)	$ 0.97	$ 1.03
Vested, restricted stock units, shares (in shares)	(50,002)	(605,630)
Vested, restricted stock units, weighted average grant date fair value (in dollars per share)	$ 1.50	$ 1.09
Ending balance, unvested restricted stock units, shares (in shares)	45,003	100,005
Ending balance, unvested restricted stock units, weighted average grant date fair value (in dollars per share)	$ 1.51	$ 1.50