Port for the Durango-X home computer of the 'Columns' puzzle game by Jay Geertsen and popularised by SEGA.
To build, simply assemble columns.s with xa65 or other suitable assembler:
xa columns.s -o columns.dux
This will normally generate a ROM image (usuaully .dux) which can be used to blow an actual (E)EPROM, or stored into an SD card for the bootloader, which needs a ShadowRAM/Development cartridge; but a Pocket executable can be generated as well, to be downloaded from a RaspberryPi thru the nanoBoot protocol, or again stored on SD for execution (bootloader 2.1.8 or later recommended):
xa columns.s -o columns.px -DPOCKET
For convenience, there are (mostly recent) prebuilt files on both formats inside the bin/ folder