Summary of significant accounting policies, Revenue recognition - Contract balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Summary of significant accounting policies [Abstract]
Revenue recognized	$ 1,400
Net contract (liabilities) assets [Abstract]
Unbilled receivables, current	145	$ 392
Unbilled receivables, non-current	120	163
Customer pre-payments	(155)	(101)
Deferred revenue, current	(1,079)	(1,329)
Deferred revenue, non-current	(209)	(143)
Net contract (liabilities) assets	$ (1,178)	$ (1,018)