Note 12 - Equity Transactions and Stock-based Compensation - Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range (Details) - $ / shares	12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2020
Range of Exercise Price, Lower Limit (in dollars per share)	$ 0.09
Range of Exercise Price, Upper Limit (in dollars per share)	$ 1.05
Outstanding (in shares)	4,443,933	3,916,666	3,344,000
Weighted average exercise price (in dollars per share)	$ 0.36	$ 0.26	$ 0.16
Weighted Average Remaining Contractual Life (Year)	7 years
Exercisable (in shares)	3,524,500	3,114,099
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.26	$ 0.19
Range One [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.09
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.10
Outstanding (in shares)	1,296,000
Weighted average exercise price (in dollars per share)	$ 0.09
Weighted Average Remaining Contractual Life (Year)	2 years 10 months 24 days
Exercisable (in shares)	1,296,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.09
Range Two [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.21
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.21
Outstanding (in shares)	1,209,000
Weighted average exercise price (in dollars per share)	$ 0.21
Weighted Average Remaining Contractual Life (Year)	6 years 10 months 24 days
Exercisable (in shares)	1,209,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.21
Range Three [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.23
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.25
Outstanding (in shares)	450,000
Weighted average exercise price (in dollars per share)	$ 0.23
Weighted Average Remaining Contractual Life (Year)	4 years 4 months 24 days
Exercisable (in shares)	450,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.23
Range Four [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.51
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.51
Outstanding (in shares)	200,000
Weighted average exercise price (in dollars per share)	$ 0.51
Weighted Average Remaining Contractual Life (Year)	10 years
Exercisable (in shares)	0
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0
Range Five [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.65
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.65
Outstanding (in shares)	601,333
Weighted average exercise price (in dollars per share)	$ 0.65
Weighted Average Remaining Contractual Life (Year)	8 years 4 months 24 days
Exercisable (in shares)	298,667
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.65
Range Six [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.72
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.72
Outstanding (in shares)	150,000
Weighted average exercise price (in dollars per share)	$ 0.72
Weighted Average Remaining Contractual Life (Year)	5 years 10 months 24 days
Exercisable (in shares)	83,333
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.72
Range Seven [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.95
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.95
Outstanding (in shares)	435,100
Weighted average exercise price (in dollars per share)	$ 0.95
Weighted Average Remaining Contractual Life (Year)	9 years 4 months 24 days
Exercisable (in shares)	150,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.95
Range Eight [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	1.05
Range of Exercise Price, Upper Limit (in dollars per share)	$ 1.05
Outstanding (in shares)	102,500
Weighted average exercise price (in dollars per share)	$ 1.05
Weighted Average Remaining Contractual Life (Year)	6 years 10 months 24 days
Exercisable (in shares)	37,500
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 1.05