Note 8 - Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Outstanding, options (in shares)	5,378
Outstanding, weighted average exercise price (in dollars per share)	$ 3.89
Outstanding, weighted average remaining contractual term (Year)	8 years 3 months 7 days	8 years 2 months 26 days
Outstanding, aggregate intrinsic value	$ 92	$ 6,316
Granted, options (in shares)	2,688
Granted, weighted average exercise price (in dollars per share)	$ 3.76
Granted, weighted average remaining contractual term (Year)	9 years 4 months 6 days
Exercised, options (in shares)	(29)
Exercised, weighted average exercise price (in dollars per share)	$ 1.75
Forfeited/canceled, options (in shares)	(274)
Forfeited/canceled, weighted average exercise price (in dollars per share)	$ 4.29
Outstanding, options (in shares)	7,763	5,378
Outstanding, weighted average exercise price (in dollars per share)	$ 3.84	$ 3.89
Vested, options (in shares)	3,580
Vested, weighted average exercise price (in dollars per share)	$ 4.28
Vested, weighted average remaining contractual term (Year)	7 years 7 months 6 days
Vested, aggregate intrinsic value	$ 34		$ 19