Here it is! This is the game I've been working on the past couple months, that I showed off at Fest West '17 earlier today. I wanted something to learn assembly by porting a NES classic to the TI99/4a. I'm using graphics mode 1 with almost all 256 tile patterns used. The graphics were done in Magellan. The assembly is compiled using RalphB's excellent xdt99 tools. The music was imported using NSFImport and FamiTracker which can export the music notes to a text file, which I then converted to bytes to play on the sound chip.
I used Classic99 for testing during development, and its very valuable debugger. When writing assembly I have to step through it in the debugger the first time to figure out why it doesn't work right. I got to try it on actual iron for the first time today thanks to iKarith and Airshack, and discovered that it worked fine on the F18A but there were graphical glitches on the stock VDP chip. Turns out I was reading from the VDP too quickly and putting a NOP between the address and the read fixed it (just like the E/A manual says to do.)
The game is a work in progress: all the secret entrances are exposed, all the caves are empty, there are no enemies or items yet, the dungeons shouldn't be caves (but I have the dungeon tileset drawn already) but it is possible to explore all 16x8 screens and swing your sword at rocks and stuff. A joystick is optional, can use WASD to move and Enter is attack. The rom is 32k (4 banks) and has no expansion requirements. I would have been so happy to play something like this back in the 80's.