Note 6 - Stockholders' Equity (Deficiency) - Summary of Warrant Activity (Details) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Outstanding, number of options (in shares)	5,219,163
Granted (in shares)
Exercised (in shares)	(1,215,000)
Exercised, weighted average exercise price (in dollars per share)	$ (0.50)
Expired, unexercised (in shares)	(1,002,668)
Expired, unexercised, weighted average exercise price (in dollars per share)	$ (0.48)
Outstanding, number of options (in shares)	3,001,495	5,219,163
Outstanding, weighted average exercise price (in dollars per share)	$ 0.52	$ 0.48
Warrants with June 15, 2018 Expiration Date [Member]
Granted (in shares)		2,323,779
Exercised (in shares)		(121,111)
Exercised, weighted average exercise price (in dollars per share)		$ (0.43)
Warrants with June 15, 2018 Expiration Date [Member] | Minimum [Member]
Granted, weighted average exercise price (in dollars per share)		0.43
Warrants with June 15, 2018 Expiration Date [Member] | Maximum [Member]
Granted, weighted average exercise price (in dollars per share)		$ 0.49
Warrants with September 28, 2018 Expiration Date [Member]
Granted (in shares)		2,887,895
Warrants with September 28, 2018 Expiration Date [Member] | Minimum [Member]
Granted, weighted average exercise price (in dollars per share)		$ 0.44
Warrants with September 28, 2018 Expiration Date [Member] | Maximum [Member]
Granted, weighted average exercise price (in dollars per share)		$ 0.52
Warrants with October 26, 2018 Expiration Date [Member]
Granted (in shares)		128,600
Warrants with October 26, 2018 Expiration Date [Member] | Minimum [Member]
Granted, weighted average exercise price (in dollars per share)		$ 0.44
Warrants with October 26, 2018 Expiration Date [Member] | Maximum [Member]
Granted, weighted average exercise price (in dollars per share)		$ 0.52