Note 10 - Equity Incentive Plans - Summary of Stock Option and RSU Transactions (Details) - $ / shares	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Shares available for grant, balance (in shares)	12,074,692
Number of options outstanding, beginning balance (in shares)	14,725,261
Weighted average exercise price, balance (in dollars per share)	$ 4.48
Shares available for grant, granted (in shares)	(10,631,320)
Number of options outstanding, granted (in shares)	7,399,849
Weighted average exercise price, granted (in dollars per share)	$ 0.78
Number of options outstanding, exercised (in shares)	(54,720)	(166,993)
Weighted average exercise price, exercised (in dollars per share)	$ 0.31
Number of options outstanding, Released (in shares)	0
Weighted average exercise price, released (in dollars per share)	$ 0
Shares available for grant, forfeited (in shares)	2,347,716
Number of options outstanding, forfeited (in shares)	(2,066,399)
Weighted average exercise price, forfeited (in dollars per share)	$ 5.08
Shares available for grant, canceled (in shares)	1,736,253
Number of options outstanding, canceled (in shares)	(1,930,082)
Weighted average exercise price, canceled (in dollars per share)	$ 4.48
Shares available for grant, balance (in shares)	5,527,341
Number of options outstanding, balance (in shares)	18,073,909
Weighted average exercise price, balance (in dollars per share)	$ 2.91
Restricted Stock Units (RSUs) [Member]
Number of RSUs outstanding (in shares)	808,310
Balance, Weighted average grant date fair value (in dollars per share)	$ 3.57
GrantedNumber of RSUs outstanding, granted (in shares)	3,231,471
Granted, Weighted average grant date fair value (in dollars per share)	$ 0.78
Number of RSUs outstanding, exercised (in shares)	0
Exercised, Weighted average grant date fair value (in dollars per share)	$ 0
Number of RSUs outstanding, released (in shares)	(163,766)
Released, Weighted average grant date fair value (in dollars per share)	$ 3.82
Number of RSUs outstanding, forfeited (in shares)	(281,317)
Forfeited, Weighted average grant date fair value (in dollars per share)	$ 2.53
Number of RSUs outstanding (in shares)	3,594,698
Balance, Weighted average grant date fair value (in dollars per share)	$ 1.13