Note 8 - Stock Based Compensation - Summary of Intrinsic Value (Details) - USD ($)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Outstanding, numbre of shares underling options (in shares)	12,916	17,082	29,165
Outstanding, weighted average exercise price per share (in dollars per share)	$ 5.47	$ 6.10	$ 7.20
Outstanding, weighted average remaining contractual life (Year)	6 years 2 months 23 days
Outstanding, aggregate intrinsic value	$ 189,765
Exercisable, numbre of shares underling options (in shares)	12,916
Exercisable, weighted average exercise price per share (in dollars per share)	$ 5.47
Exercisable, weighted average remaining contractual life (Year)	6 years 2 months 23 days
Exercisable, aggregate intrinsic value	$ 189,765

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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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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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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