Note 9 - Share-based Compensation - Summary of Option Activity Under Stock Plans (Details) - USD ($)	6 Months Ended	12 Months Ended
Sep. 30, 2024	Mar. 31, 2024
Outstanding (in shares)	297,000
Outstanding, weighted average exercise price (in dollars per share)	$ 2.47
Outstanding, weighted average remaining contractual term (Year)	6 years 8 months 12 days	7 years 1 month 6 days
Granted (in shares)	50,000
Granted, weighted average exercise price (in dollars per share)	$ 0.78
Outstanding (in shares)	347,000	297,000
Outstanding, weighted average exercise price (in dollars per share)	$ 2.23	$ 2.47
Outstanding, aggregate intrinsic value	$ 0
Exercisable (in shares)	247,000
Exercisable, weighted average exercise price (in dollars per share)	$ 2.64
Exercisable, weighted average remaining contractual term (Year)	5 years 7 months 6 days

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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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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-Topic 718
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-Publisher FASB
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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 per share amount at which grantees can acquire shares of common stock by exercise of options.

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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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