Note 7 - Stockholders' Equity - Stock Options Activity (Details) - USD ($)	12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019
Outstanding, options (in shares)	9,511,600	7,411,600
Outstanding, weighted-average exercise price (in dollars per share)	$ 0.74	$ 1.08
Outstanding, weighted-average remaining contractual life (Year)	3 years 255 days	4 years 182 days	3 years 36 days
Outstanding, aggregate intrinsic value	$ 6,064,335		$ 20,375
Granted, options (in shares)	960,000	2,210,000
Granted, weighted-average exercise price (in dollars per share)	$ 1.10	$ 0.72
Exercised, options (in shares)
Exercised, weighted-average exercise price (in dollars per share)
Forfeited, options (in shares)
Forfeited, weighted-average exercise price (in dollars per share)
Expired, options (in shares)		(110,000)
Expired, weighted-average exercise price (in dollars per share)		$ 0.69
Outstanding at June 30, 2020 (in shares)	10,471,600	9,511,600	7,411,600
Outstanding, weighted-average exercise price (in dollars per share)	$ 0.77	$ 0.74	$ 1.08
Exercisable, options (in shares)	10,471,600
Exercisable, weighted-average exercise price (in dollars per share)	$ 0.77
Exercisable, weighted-average remaining contractual life (Year)	3 years 255 days
Exercisable, aggregate intrinsic value	$ 6,064,335