  The detection of astrophysical Gamma-Ray Bursts (GRBs) has always been
intertwined with the challenge of identifying the direction of the source.
Accurate angular localization of better than a degree has been achieved to date
only with heavy instruments on large satellites, and a limited field of view.
The recent discovery of the association of GRBs with neutron star mergers gives
new motivation for observing the entire $\gamma$-ray sky at once with high
sensitivity and accurate directional capability. We present a novel
$\gamma$-ray detector concept, which utilizes the mutual occultation between
many small scintillators to reconstruct the GRB direction. We built an
instrument with 90 (9\,mm)$^3$ \csi~scintillator cubes attached to silicon
photomultipliers. Our laboratory prototype tested with a 60\,keV source
demonstrates an angular accuracy of a few degrees for $\sim$25 ph\,cm$^{-2}$
bursts. Simulations of realistic GRBs and background show that the achievable
angular localization accuracy with a similar instrument occupying $1$l volume
is $<2^\circ$. The proposed concept can be easily scaled to fit into small
satellites, as well as large missions.
