Note 9 - Share-based Compensation - Summary of Option Activity Under Stock Plans (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2022	Mar. 31, 2022
Outstanding (in shares)	252,500
Outstanding, weighted average exercise price (in dollars per share)	$ 3.34
Outstanding, weighted average remaining contractual term (Year)	6 years 10 months 24 days	6 years 6 months
Outstanding, aggregate intrinsic value	$ 78,400	$ 159,650
Granted (in shares)	50,000
Granted, weighted average exercise price (in dollars per share)	$ 3.43
Outstanding (in shares)	302,500	252,500
Outstanding, weighted average exercise price (in dollars per share)	$ 3.36	$ 3.34
Exercisable (in shares)	127,500
Exercisable, weighted average exercise price (in dollars per share)	$ 4.17
Exercisable, weighted average remaining contractual term (Year)	4 years 3 months 18 days
Exercisable, aggregate intrinsic value	$ 25,316