Working through the game start up and it's a bit of a grind to be honest. A fair bit of code had to be transcribed before anything interesting happened. But I now have the game starting and the player ship moving around. If you don't die from being hit or colliding with something, you'll run out of fuel.
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| Coin up, start a game and move around. |
No shooting or bombing, but you can play through the 3 lives and it displays "GAME OVER" although I suspect the scroll offsets of the display area haven't been reset as they should be as it appears at a random offset from centre, and in the wrong colour. A quick search didn't reveal where that was but I'll find it.
As I work through the code I mark each routine as being one of UNIMPLEMENTED, WIP, LOOKS_OK, UNTESTED or COMPLETE via a printf that can be selectively enabled or disabled by category. Today added a whole swag of UNTESTED routines.
Unlike my earlier efforts, in this transcode I've started with the original disassembly, with every line denoted a C comment. Makes it much easier to keep functions in the same order as the ASM code, and keep track of addresses etc. Until a few days ago I was writing the new C function under the corresponding ASM function, but more recently I've moved the commented ASM inside the functions with the C code following each block of ASM code.
I've been removing the ASM code from the file whenever I deem a function to be COMPLETE (tested, debugged) but now I'm thinking that in my next transcode, I should actually keep the ASM code in there. It'll blow out the source file size of course, but does that really matter?
// $10BA
void game_init (void)
{
DEBUG_OPT_UNTESTED;
//10BA: 21 09 40 ld hl,$4009 ; load HL with address of TEMP_COUNTER_4009
//10BD: 35 dec (hl)
//10BE: C0 ret nz ; wait until counter reaches zero
//10BF: 36 0A ld (hl),$0A ; set TEMP_COUNTER_4009 to 10
if (--wram.temp_counter_4009 != 0)
return;
wram.temp_counter_4009 = 10;
//10C1: 2C inc l ; bump HL to point to SCRIPT_STAGE
//10C2: 34 inc (hl) ; advance to next stage of script (PLAY_GAME @ $22F4)
wram.script_stage++;
//10C3: 3E 01 ld a,$01
//10C5: 32 19 40 ld ($4019),a ; set DRAW_LANDSCAPE_FLAG
wram.draw_landscape_flag = 1;
//10C8: 21 01 00 ld hl,$0001
//10CB: 22 80 43 ld ($4380),hl ; set PLAYERS[0].IsActive and reset PLAYERS[0].IsExploding flags
//10CE: 22 A0 43 ld ($43A0),hl ; set PLAYERS[1].IsActive and reset PLAYERS[1].IsExploding flags
wram.players[0].is_active = 1;
wram.players[0].is_exploding = 0;
wram.players[1].is_active = 1;
wram.players[1].is_exploding = 0;
//10D1: AF xor a
//10D2: 32 82 43 ld ($4382),a ; reset PLAYERS[0].StageOfLife (see PLAYER_INIT @ $16FE)
wram.players[0].stage_of_life = 0;
//; player starting level, update lives remaining
//10D5: 21 08 41 ld hl,$4108 ; load HL with address of CURRENT_PLAYER_LIVES
//10D8: 35 dec (hl) ; reduce number of lives
//10D9: 11 03 07 ld de,$0703 ; Command ID: 7 = HEAD_UP_DISPLAY_COMMAND, Param:3 = DISPLAY_CURRENT_PLAYER_LIVES
//10DC: FF rst $38 ; call QUEUE_COMMAND
wram.current_player_lives--;
rst38_queue_command (7, 3); // HEAD_UP_DISPLAY_COMMAND, CURRENT_PLAYER_LIVES
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