Note 5 - Computation of Net Loss Per Common Share - Reconciliation of Numerators and Denominators of EPS Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Net loss	$ (9,881)	$ (8,710)	$ (4,434)	$ (5,403)	$ (18,590)	$ (9,837)
Weighted-average shares of common stock outstanding (in shares)	28,775		28,360		28,648	28,141
Weighted-average shares subject to repurchase (in shares)	(908)		(1,108)		(934)	(1,101)
Shares used in per-share calculation ? basic (in shares)	27,867		27,252		27,714	27,040
Shares used in per-share calculation ? diluted (in shares)	27,867		27,252		27,714	27,040
Net loss per share ? basic (in dollars per share)	$ (0.35)		$ (0.16)		$ (0.67)	$ (0.36)
Net loss per share ? diluted (in dollars per share)	$ (0.35)		$ (0.16)		$ (0.67)	$ (0.36)