Note 6 - Stockholders' Equity - Common Stock Reserved for Future Issuance (Details)	Mar. 31, 2022 shares
Shares reserved (in shares)	9,578,808
Warrant [Member]
Shares reserved (in shares)	5,109,501
Share-Based Payment Arrangement, Option [Member]
Shares reserved (in shares)	2,444,136
Restricted Stock Units (RSUs) [Member]
Shares reserved (in shares)	5,395
Shares Available for Grant Under Equity Incentive Plan [Member]
Shares reserved (in shares)	2,019,776