Note 2 - Fair Value Measurements 1 (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2024

Dec. 31, 2023

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Fair Value Measured as of March 31, 2024 Using:
	Adjusted Cost		Unrealized losses			Fair Value		Cash and Cash Equivalent		Marketable Securities
Assets
Level 1
Money market funds	$	8,761	$	—		$	8,761	$	8,761	$	—
Level 2
Corporate bonds		7,493		(3	)		7,490		—		7,490
Commercial paper		7,907		(1	)		7,906		—		7,906
U.S. Government securities		3,978		—			3,978		—		3,978
Total financial assets	$	28,139	$	(4	)	$	28,135	$	8,761	$	19,374
Liabilities
Level 2
Private placement warrant liability	$	—	$	—		$	—	$	—	$	—
Level 3
Derivative warrant liability		—		—			24		—		—
Total financial liabilities	$	—	$	—		$	24	$	—	$	—

	Fair Value Measured as of December 31, 2023 Using:
	Adjusted Cost		Unrealized gains		Fair Value		Cash and Cash Equivalent		Marketable Securities
Assets
Level 1
Money market funds	$	16,377	$	—	$	16,377	$	16,377	$	—
Level 2
Corporate bonds		2,880		1		2,881		—		2,881
Commercial paper		8,809		5		8,814		—		8,814
U.S. Government securities		7,892		4		7,896		—		7,896
Total financial assets	$	35,958	$	10	$	35,968	$	16,377	$	19,591
Liabilities
Level 2
Private placement warrant liability	$	—	$	—	$	—	$	—	$	—
Level 3
Derivative warrant liability		—		—		26		—		—
Total financial liabilities	$	—	$	—	$	26	$	—	$	—

	Fair Value Measured as of December 31, 2023 Using:
	Adjusted Cost		Unrealized gains		Fair Value		Cash and Cash Equivalent		Marketable Securities
Assets
Level 1
Money market funds	$	16,377	$	—	$	16,377	$	16,377	$	—
Level 2
Corporate bonds		2,880		1		2,881		—		2,881
Commercial paper		8,809		5		8,814		—		8,814
U.S. Government securities		7,892		4		7,896		—		7,896
Total financial assets	$	35,958	$	10	$	35,968	$	16,377	$	19,591
Liabilities
Level 2
Private placement warrant liability	$	—	$	—	$	—	$	—	$	—
Level 3
Convertible notes		—		—		—		—		—
Derivative warrant liability		—		—		26		—		—
Total financial liabilities	$	—	$	—	$	26	$	—	$	—

	Fair Value Measured as of December 31, 2022 Using:
	Adjusted Cost		Unrealized losses			Fair Value		Cash and Cash Equivalent		Marketable Securities
Assets
Level 1
Money market funds	$	14,253	$	—		$	14,253	$	14,253	$	—
Level 2
Asset-backed securities		3,507		(119	)		3,388		—		3,388
Corporate bonds		22,139		(240	)		21,899		—		21,899
Commercial paper		20,760		—			20,760		—		20,760
U.S. Government securities		29,983		(895	)		29,088		—		29,088
Total financial assets	$	90,642	$	(1,254	)	$	89,388	$	14,253	$	75,135
Liabilities
Level 2
Private placement warrant liability	$	—	$	—		$	7	$	—	$	—
Level 3
Convertible notes		—		—			8,594		—		—
Derivative warrant liability		—		—			119		—		—
Total financial liabilities	$	—	$	—		$	8,720	$	—	$	—

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

	Derivative Warrant Liability
Balance at December 31, 2023	$	26
Change in fair value included in other income (expense), net		(2	)
Balance at March 31, 2024	$	24

	2022 Convertible Note			Derivative Warrant Liability			Total
Balance at December 31, 2022	$	8,594		$	119		$	8,713
Additions		—			—			—
Payments or conversions		(9,573	)		—			(9,573	)
Change in fair value included in other income (expense), net		958			(93	)		865
Change in fair value due to instrument specific credit risk included in other comprehensive income		21			—			21
Balance at December 31, 2023	$	—		$	26		$	26

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

	March 31, 2024
Expected term (years)		2.4
Expected volatility		234.8	%
Risk-free interest rate		4.5	%
Dividend yield		—	%
Exercise price	$	105.00

	December 31, 2023
Expected term (years)		2.7
Expected volatility		155.7	%
Risk-free interest rate		4.1	%
Dividend yield		—	%
Exercise price	$	105.00