Note 3 - Revenue - Costs, Estimated Earnings, and Billings on Uncompleted Contracts (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Costs incurred on contracts in progress	$ 4,464,471	$ 6,943,066
Estimated earnings	2,087,396	3,370,032
Costs and Estimated Earnings on Uncompleted Contracts	6,551,867	10,313,098
Billings to date	(6,212,229)	(10,645,800)
Net Cost in Excess of Billings	339,638	(332,702)
Deferred revenue related to non-systems contracts	(632,014)	(1,429,582)
Contract Liability In Excess of Contract Assets	(292,376)	(1,762,284)
Included in accompanying balance sheets
Contract with Customer, Asset, after Allowance for Credit Loss, Total	494,281	512,952	$ 1,400,000
Contract liabilities	$ (786,657)	$ (2,275,236)	$ (500,000)