Ok I finally got some free time to try the z80 entries. I commented in some threads but I'll sum things up here with 6 small reviews:
-CYANOID
Nice looking entry with smooth speed. Kinda repetitive after a while and it's hard to pass between walls.
-Embers-Phoenix
My favorite entry of all, nice graphics and gameplay. Only issues are glitched maps (at the top or bottom, there is garbage sometimes when moving too far there) and the boss hit detection. Also the sword is hard to find and get.
-M.E.T.A.
My second favorite entry, also some nice graphics and power ups. However the difficulty was a bit too easy since if you stood behind the boss to shoot at him, you didn't take any hit and the ball power up (F3) was a bit OP. 
-Vortex 15
Interesting entry with awesome AI. However I found the difficulty a bit too hard, even in easy mode. I actually won once, but I never managed to figure out how to do things such as getting money to buy items and grab what's inside treasure chests. Shooting at the latter just destroyed them with no reward.
-ZAMPO!
Never managed to figure out how to play. Graphics looked nice, though.
-Rock Paper Scissors
Never figured out how to play RPS. Just kidding lol. The game itself was simple but just the achievement system reminded me of a Flash game I played once and if it wasn't for getting repetitive fast, it would have made it to my top 3. Easily the most original RPS clone out there.
I think a lot of work was put in all those entries considering the very limited amount of time people had to finish them. 
For META, there was 3 patterns for boss: Ramming, shooting stuff through 8 directions, and laz0rs. Actually, there's even more OP way to kill it, and that's using MetaBox
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