| Routines

55A0: Count down from 9 to 0

Continues from the routine at 81B4. Counts down from 9 to 0, giving the user a chance to set the input method and change the characters' names before the game starts.
Input
BC | 0100
DE | 8100
HL | 5B00
55A0 | LDIR | Copy 256 bytes from 5B00 to 8100
55A2 | LD H,$58 | INK 1: PAPER 1
55A4 | LD B,$03
55A6 | LD D,H
55A7 | INC E
55A8 | LD (HL),$09
55AA | LDIR
55AC | LD HL,$5C3B | Reset bit 5 at 5C3B, ready for future keypresses
55AF | RES 5,(HL)
55B1 | EXX | Point HL' at the last byte of the graphic data for the digit '9' in the ROM
55B2 | LD HL,$3DCF
55B5 | EXX
55B6 | LD DE,$043C | Wait approximately one second
55B9 | DJNZ $55B9
55BB | DEC DE
55BC | LD A,D
55BD | OR E
55BE | JR NZ,$55B9
55C0 | LD HL,$59EC | 59EC is the attribute file address where the bottom row of 'big pixels' will be drawn
55C3 | LD DE,$FFD8 | DE=-40
55C6 | LD C,$08 | There are 8 pixel rows per countdown digit
55C8 | EXX |
55C9 | BIT 7,L | Set the zero flag when HL' hits 3D7F
55CB | LD A,(HL) | Pick up a digit pixel row byte
55CC | DEC HL | Move HL' to the next pixel row up
55CD | EXX |
55CE | JP Z,$54E9 | Start the game if we've already printed '0'
55D1 | LD B,$08 | There are 8 bits per pixel row
55D3 | LD (HL),$09 | INK 1: PAPER 1 (blue) for a reset pixel
55D5 | RLCA | Is this a reset pixel?
55D6 | JR NC,$55DA | Jump if so
55D8 | LD (HL),$24 | INK 4: PAPER 4 (green) for a set pixel
55DA | INC HL | Move HL along to the next attribute file address
55DB | DJNZ $55D3 | Jump back until all 8 'big pixels' have been drawn
55DD | ADD HL,DE | Move HL back 8 spaces and up one row of the attribute file
55DE | DEC C | Next pixel row
55DF | JR NZ,$55C8 | Jump back until all 8 pixel rows have been drawn
55E1 | CALL $7154 | Make a ticking sound effect
55E4 | LD HL,$5C3B |
55E7 | BIT 5,(HL) | Reset the zero flag if a key was pressed
55E9 | RES 5,(HL) | Reset bit 5 at 5C3B, ready for future keypresses
55EB | JP NZ,$53B1 | Jump if a key was pressed
55EE | JR $55B6 | Wait roughly one second, then print the next digit