Note 8 - Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Outstanding, options (in shares)	7,876
Outstanding, weighted average exercise price (in dollars per share)	$ 3.81
Outstanding, weighted average remaining contractual term (Year)	8 years 4 months 28 days	8 years 18 days
Outstanding, aggregate intrinsic value	$ 627	$ 11
Granted, options (in shares)	3,440
Granted, weighted average exercise price (in dollars per share)	$ 1.83
Granted, weighted average remaining contractual term (Year)	9 years 9 months 18 days
Exercised, options (in shares)	0
Exercised, weighted average exercise price (in dollars per share)	$ 0
Forfeited/canceled, options (in shares)	0
Forfeited/canceled, weighted average exercise price (in dollars per share)	$ 0
Outstanding, options (in shares)	11,316	7,876
Outstanding, weighted average exercise price (in dollars per share)	$ 3.21	$ 3.81
Vested, options (in shares)	4,447
Vested, weighted average exercise price (in dollars per share)	$ 4.1
Vested, weighted average remaining contractual term (Year)	7 years 3 months 29 days
Vested, aggregate intrinsic value	$ 60		$ 500