Note 8 - Stockholders' Equity - Summary of Option Activity for Employees and Non-employees (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Number of options, granted (in shares)	0
Weighted average exercise price, granted (in dollars per share)	$ 0
Share-Based Payment Arrangement, Option [Member] \| Share-Based Payment Arrangement, Employee [Member]
Number of options (in shares)	2,843,693
Weighted average exercise price, outstanding (in dollars per share)	$ 2.39
Weighted average remaining contractual life, outstanding (Year)	7 years 4 months 9 days	7 years 8 months 8 days
Aggregate intrinsic value, outstanding	$ 0	$ 49,246
Number of options, granted (in shares)	216,296
Weighted average exercise price, granted (in dollars per share)	$ 1.52
Number of options, exercised (in shares)	0
Weighted average exercise price, exercised (in dollars per share)	$ 0
Number of options, forfeited or expired (in shares)	0
Weighted average exercise price, forfeited or expired (in dollars per share)	$ 0
Number of options (in shares)	3,059,989	2,843,693
Weighted average exercise price, outstanding (in dollars per share)	$ 2.37	$ 2.39
Number of options exercisable (in shares)	594,914
Weighted average exercise price, exercisable (in dollars per share)	$ 1.98
Weighted average remaining contractual life, exercisable (Year)	3 years 9 months 18 days
Aggregate intrinsic value, exercisable	$ 0
Share-Based Payment Arrangement, Option [Member] \| Share-Based Payment Arrangement, Nonemployee [Member]
Number of options (in shares)	83,330
Weighted average exercise price, outstanding (in dollars per share)	$ 1.85
Weighted average remaining contractual life, outstanding (Year)	3 years 29 days	3 years 3 months 29 days
Aggregate intrinsic value, outstanding	$ 22,585	$ 49,748
Number of options, exercised (in shares)	0
Weighted average exercise price, exercised (in dollars per share)	$ 0
Number of options (in shares)	83,330	83,330
Weighted average exercise price, outstanding (in dollars per share)	$ 1.85	$ 1.85
Number of options exercisable (in shares)	63,883
Weighted average exercise price, exercisable (in dollars per share)	$ 1.68
Weighted average remaining contractual life, exercisable (Year)	2 years 10 months 6 days
Aggregate intrinsic value, exercisable	$ 22,582

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Gross number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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