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, 2024	Jun. 30, 2023	Jun. 30, 2022
Range of Exercise Price, Lower Limit (in dollars per share)	$ 0.09
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.95
Outstanding (in shares)	4,749,183	4,376,284	4,443,933
Weighted average exercise price (in dollars per share)	$ 0.34	$ 0.35	$ 0.36
Weighted Average Remaining Contractual Life (Year)	8 years 1 month 6 days
Exercisable (in shares)	3,804,150	3,626,551
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.34	$ 0.3
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)	$ 0.09
Outstanding (in shares)	1,071,000
Weighted average exercise price (in dollars per share)	$ 0.09
Weighted Average Remaining Contractual Life (Year)	10 months 24 days
Exercisable (in shares)	1,071,000
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)	1,194,000
Weighted average exercise price (in dollars per share)	$ 0.21
Weighted Average Remaining Contractual Life (Year)	4 years 10 months 24 days
Exercisable (in shares)	1,194,000
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)	$ 0.23
Outstanding (in shares)	100,000
Weighted average exercise price (in dollars per share)	$ 0.23
Weighted Average Remaining Contractual Life (Year)	2 years 4 months 24 days
Exercisable (in shares)	100,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.23
Range Four [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.24
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.26
Outstanding (in shares)	582,500
Weighted average exercise price (in dollars per share)	$ 0.25
Weighted Average Remaining Contractual Life (Year)	9 years 4 months 24 days
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)	0.33
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.33
Outstanding (in shares)	200,000
Weighted average exercise price (in dollars per share)	$ 0.33
Weighted Average Remaining Contractual Life (Year)	9 years 1 month 6 days
Exercisable (in shares)	200,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.33
Range Six [Member]
Range of Exercise Price, Lower Limit (in dollars per share)	0.41
Range of Exercise Price, Upper Limit (in dollars per share)	$ 0.41
Outstanding (in shares)	414,334
Weighted average exercise price (in dollars per share)	$ 0.41
Weighted Average Remaining Contractual Life (Year)	8 years 1 month 6 days
Exercisable (in shares)	140,334
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.41
Range Seven [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)	8 years
Exercisable (in shares)	200,000
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.51
Range Eight [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)	566,333
Weighted average exercise price (in dollars per share)	$ 0.65
Weighted Average Remaining Contractual Life (Year)	6 years 4 months 24 days
Exercisable (in shares)	566,333
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.65
Range Nine [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)	421,016
Weighted average exercise price (in dollars per share)	$ 0.95
Weighted Average Remaining Contractual Life (Year)	7 years 1 month 6 days
Exercisable (in shares)	332,483
Weighted Average Exercise Price, Exercisable (in dollars per share)	$ 0.95