Note 9 - Stockholders' Equity (Details Textual) - USD ($) | Jun. 07, 2021 | Feb. 11, 2021 | Feb. 28, 2021 | Jun. 30, 2021 | Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2020 |
Stock Repurchased During Period, Value | | | | $ 1,000 | | | |
Stock Issued During Period, Shares, New Issues (in shares) | | 1,644,000 | | | | | |
Shares Issued, Price Per Share (in dollars per share) | | $ 6.25 | | | | | |
Proceeds from Issuance of Common Stock | | $ 9,400,000 | | | $ 9,408,920 | $ 0 | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares) | | | | | 0 | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares) | | | | 602,000 | 602,000 | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price, Ending Balance (in dollars per share) | | | | $ 2.79 | $ 2.79 | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year) | | | | | 9 years 4 months 24 days | | |
Proceeds from Warrant Exercises | | | $ 3,174,156 | | $ 3,174,156 | $ 0 | |
Stock Issued During Period, Shares, Issued for Services (in shares) | | | | | 13,707 | | |
Stock Incentive Plan 2020 [Member] | | | | | | | |
Common Stock, Capital Shares Reserved for Future Issuance (in shares) | | | | 1,500,000 | 1,500,000 | | |
Representative Warrants [Member] | | | | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | | 72,000 | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | $ 6.875 | | | | | |
Class of Warrant or Right, Period for Warrants or Rights Exercisable (Day) | | 180 days | | | | | |
Warrants and Rights Outstanding, Term (Year) | | 3 years | | | | | |
Stock Purchase Warrants First Issuance [Member] | | | | | | | |
Class of Warrant or Right, Exercised During Period (in shares) | | | 188,688 | | 188,668 | | |
Stock Issued During Period, Shares, Warrants Exercised (in shares) | | | 145,866 | | 145,866 | | |
Stock Purchase Warrants Second Issuance [Member] | | | | | | | |
Class of Warrant or Right, Exercised During Period (in shares) | | | 690,034 | | | | |
Stock Issued During Period, Shares, Warrants Exercised (in shares) | | | 690,034 | | | | |
Stock Purchase Warrants [Member] | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | | | | $ 5.07 | $ 5.07 | | |
Warrants and Rights Outstanding, Term (Year) | | | | 4 years 1 month 6 days | 4 years 1 month 6 days | | |
Class of Warrant or Right, Outstanding (in shares) | | | | 2,793,635 | 2,793,635 | | |
Over-Allotment Option [Member] | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | | 204,000 | | | | | |
Series B Convertible Preferred Stock [Member] | | | | | | | |
Stock Repurchased During Period, Shares (in shares) | 100 | | | | | | |
Stock Repurchased During Period, Value | $ 1,000 | | | | | | |
Preferred Stock, Shares Outstanding, Ending Balance (in shares) | | | | 0 | 0 | | 100 |