Stock options (Tables)

12 Months Ended

Dec. 31, 2022

Stock options

Stock option activity

	Year ended December 31,
	2022						2021					2020
	Number of options			Weighted average exercise price			Number of options		Weighted average exercise price			Number of options		Weighted average exercise price
				US$					US$					US$
Outstanding, beginning of year		85,000			1.56			51,000		2.60			51,000		2.60
Granted		80,000			2.8			-		-			-		-
Cancelled		(41,250	)		(1.04	)		-		-			-		-
Bonus shares adjustment		82,500			(0.72	)		34,000		(1.04	)		-		-
Outstanding, end of year		206,250			1.52			85,000		1.56			51,000		2.60
Exercisable, end of year		86,250			1.04			-		-			-		-