  A high-pressure xenon gas time projection chamber, with a unique cellular
readout structure based on electroluminescence, has been developed for a
large-scale neutrinoless double-beta decay search. In order to evaluate the
detector performance and validate its design, a 180~L size prototype is being
constructed and its commissioning with partial detector has been performed. The
obtained energy resolution at 4.0~bar is 1.73 $\pm$ 0.07% (FWHM) at 511 keV.
The energy resolution at the $^{136}$Xe neutrinoless double-beta decay Q-value
is estimated to be between 0.79 and 1.52% (FWHM) by extrapolation.
Reconstructed event topologies show patterns peculiar to track end-point which
can be used to distinguish $0\nu\beta\beta$ signals from gamma-ray backgrounds.
