Note 8 - Stockholders' Equity - Stock Options Activity (Details) - USD ($)	6 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017
Outstanding, beginning balance (in shares)	4,545,037
Outstanding, weighted-average exercise price, beginning balance (in dollars per share)	$ 1.42
Outstanding, weighted-average remaining contractual life (Year)	3 years 219 days		2 years 328 days
Outstanding, aggregate intrinsic value	$ 18,025		$ 176,575
Granted, options (in shares)	295,000	294,500
Granted, weighted-average exercise price (in dollars per share)	$ 0.84
Expired, options (in shares)
Expired, weighted-average exercise price (in dollars per share)
Outstanding, ending balance (in shares)	4,840,037		4,545,037
Outstanding, weighted-average exercise price, ending balance (in dollars per share)	$ 1.39		$ 1.42
Exercisable, options (in shares)	4,735,037
Exercisable, weighted-average exercise price (in dollars per share)	$ 1.39
Exercisable, weighted-average remaining contractual life (Year)	3 years 219 days
Exercisable, aggregate intrinsic value	$ 18,025