That is really well done so far. Can't believe an Amstrad game would look that good.
To be fair I am not limiting myself to 16 colours
The only real limit is the colour palette and primarily making a game that wouldn't look out of place on your chosen computer.CPC Graphical limits : Had a palette of 27 colours but only a maximum of 16 could be used on screen.
How I read the rules is that I could create a game with 1920x1680 resolution and have use of all 27 colours of the CPC... but let's gets Qube's opinion
I'm now doing a 256 colour Speccy game
But no 8-bit system could display more than 16 colours.
I'm now doing a 256 colour Speccy game Authenticity vote = nil points
If you end up with 18 colours because a subtle shade helped a lot then you won't get your entry refused but if you use 32+ colours on screen for a C64 games then nope.
Like I said, restrictions can be too harsh and spoil graphics. I always hated the speccy colour clash and block colour - rather than pixel colour. Plus the awful sound until the 128. But no computer here could ever use more than 16 colours on-screen. Seems a shame to not at least stick to one rule.
But no computer in the 80's could ever use more than 16 colours on-screen.