Note 9 - Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Outstanding (in shares)	3,659	2,159
Outstanding, weighted average exercise price per share (in dollars per share)	$ 5.01	$ 5.00
Outstanding, weighted average remaining contractual term (Year)	8 years 2 months 26 days	8 years 11 months 23 days	9 years 8 months 8 days
Granted (in shares)	2,277	1,822
Granted, weighted average exercise price per shar (in dollars per share)	$ 2.30	$ 5.02
Granted, weighted average remaining contractual term (Year)	8 years 9 months 21 days	9 years 3 months 7 days
Exercised (in shares)	(6)	0
Exercised, weighted average exercise price per shar (in dollars per share)	$ 2.26	$ 0
Forfeited/cancelled (in shares)	(552)	(322)
Forfeited/cancelled, weighted average exercise price per shar (in dollars per share)	$ 4.78	$ 5.00
Exercised, aggregate intrinsic value	$ 6
Forfeited/cancelled, aggregate intrinsic value	$ 118
Outstanding (in shares)	5,378	3,659	2,159
Outstanding, weighted average exercise price per share (in dollars per share)	$ 3.89	$ 5.01	$ 5.00
Outstanding, aggregate intrinsic value	$ 6,316
Vested (in shares)	2,710
Vested, weighted average exercise price per share (in dollars per share)	$ 4.65
Vested, weighted average remaining contractual term (Year)	7 years 7 months 13 days
Vested, aggregate intrinsic value	$ 1,216