ZX81 tetris rework attempt at 1K

Revisiting this tetris game I wrote some time ago to try to get it to run on an expanded ZX81. I have so far in this version reached 1053bytes for the .p file. But along the way added extra features like a high score and 3 digit scoring - my high score so far is a measly 22!!! so optimistic having a max of 999.

I started this after buying the excellent book by Dr.Beep - The Ultimate 1K ZX81 coding book (how to fully use the 1K ZX81. It cost about £6 on amazon and is excellent if you want to hone your assembly language skills and write better code - I highly recommend it. It dives straight in so you do need some previous experience writing assembly code for the Z80.

My initial optimising for 1K includes:
1) using xor a to save 1 byte to zero a, rather than ld a,0
2) using jump relative wherever possible (jr) rather than jp
3) ditching several subroutines like printstring (was only used to clear the play area and print game over - now done in a loop and use flashing xxxxxx to show end of game. printnumber was used for printing the score but can use dr.beep's book idea of using the screen to store the score!
4) other general tidy up some unused code or code that doesn't add to game play like "speedup" and change colour of the blocks when they rotate.

My source code is on github at:
https://github.com/AdrianPilko/ZX81-1...