Receivables: (Details) - USD ($)	12 Months Ended
	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Current receivables
Trade	$ 7,600	$ 18,000
Royalty	1,242,800	1,198,000
Other	166,500	112,200
Total current receivables	1,416,900	1,328,200
Activity in the allowance for doubtful accounts for trade receivables
Balance at beginning of year	1,600	4,300	$ 17,300
Provisions charged to expense	1,500	(200)	(3,800)
Deductions for amounts written-off	(2,900)	(2,500)	(9,200)
Balance at end of year	$ 200	$ 1,600	$ 4,300