Note 4 - Warrants (Tables)

9 Months Ended

Sep. 30, 2023

Notes Tables

Schedule of Warrants or Rights, Assumptions Used [Table Text Block]

	September 30, 2023	December 31, 2022
Risk-free interest rate	5.1% to 5.6%	4.2% to 4.8%
Volatility	69.1% to 89.8%	63.1% to 76.3%
Expected life (years)	0.2 to 1.9	0.1 to 2.6
Dividend yield	—%	—%

Schedule of Warrant Activity [Table Text Block]

	Number of Shares			Range of Warrant Exercise				Weighted Average		Weighted Average Remaining Contractual
	Under Warrant			Price per Share				Exercise Price		Life (Years)
Balance at January 1, 2023		2,656,296		$	6.30	$	16.80	$	9.49		1.7
Expired warrants		(384,415	)	$	13.92	$	16.80	$	16.22		—
Balance at September 30, 2023		2,271,881		$	6.30	$	12.12	$	8.26		1.1
Exercisable at September 30, 2023		2,271,881		$	6.30	$	12.12	$	8.26		1.1