Note 8 - Stockholders' Equity - Summary of Warrant Activity (Details) - $ / shares |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2022 |
Dec. 31, 2021 |
|
| Outstanding (in shares) | 1,192,085 | |
| Outstanding, weighted average exercise price (in dollars per share) | $ 3.57 | |
| Outstanding, weighted average remaining contractual life (Year) | 3 years 6 months | 3 years 9 months |
| Issued (in shares) | 0 | |
| Issued, weighted average exercise price (in dollars per share) | $ 0 | |
| Expired (in shares) | 0 | |
| Expired, weighted average exercise price (in dollars per share) | $ 0 | |
| Outstanding (in shares) | 1,192,085 | 1,192,085 |
| Outstanding, weighted average exercise price (in dollars per share) | $ 3.57 | $ 3.57 |
| Exercisable (in shares) | 1,192,085 | |
| Exercisable, weighted average exercise price (in dollars per share) | $ 3.57 | |
| Exercisable, weighted average remaining contractual life (Year) | 3 years 6 months |