Note 11 - Stock-based Compensation - Stock Option Activity (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Options, Outstanding, Number of Shares (in shares)	10,444,679
Options, Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 3.2
Options, Outstanding, Weighted Average Remaining Contractual Term (Year)	5 years 4 months 13 days	4 years 9 months 18 days
Options, Granted, Number of Shares (in shares)	5,552,790
Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)	$ 0.26
Options, Cancelled, Number of Shares (in shares)	(36,406)
Options, Expirations in Period, Weighted Average Exercise Price (in dollars per share)	$ 10.24
Outstanding at March 31, 2024 (in shares)	15,961,063	10,444,679
Outstanding at March 31, 2024 (in dollars per share)	$ 2.16	$ 3.2
Outstanding at March 31, 2024	$ 0
Vested or expected to vest at March 31, 2024 (in shares)	14,795,731
Vested or expected to vest at March 31, 2024 (in dollars per share)	$ 2.3
Vested or expected to vest at March 31, 2024 (Year)	5 years 3 months 7 days
Vested or expected to vest at March 31, 2024	$ 0
Exercisable at March 31, 2024 (in shares)	7,862,867
Exercisable at March 31, 2024 (in dollars per share)	$ 3.97
Exercisable at March 31, 2024 (Year)	4 years 3 months
Exercisable at March 31, 2024	$ 0

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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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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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-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Publisher FASB
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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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-Topic 718
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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. 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 exercise price, at which grantee can acquire shares reserved for issuance, for 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 price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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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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