329 lines
7.7 KiB
C
329 lines
7.7 KiB
C
/*
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A character-based surround-the-opponent game.
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Reads from nametable RAM to determine collisions, and also
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to help the AI avoid walls.
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For more information, see "Making Arcade Games in C".
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <nes.h>
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#include <joystick.h>
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#include "neslib.h"
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// VRAM buffer module
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#include "vrambuf.h"
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//#link "vrambuf.c"
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// link the pattern table into CHR ROM
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//#link "chr_generic.s"
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#define COLS 32
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#define ROWS 27
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// read a character from VRAM.
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// this is tricky because we have to wait
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// for VSYNC to start, then set the VRAM
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// address to read, then set the VRAM address
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// back to the start of the frame.
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byte getchar(byte x, byte y) {
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// compute VRAM read address
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word addr = NTADR_A(x,y);
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// result goes into rd
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byte rd;
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// wait for VBLANK to start
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ppu_wait_nmi();
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// set vram address and read byte into rd
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vram_adr(addr);
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vram_read(&rd, 1);
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// scroll registers are corrupt
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// fix by setting vram address
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vram_adr(0x0);
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return rd;
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}
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void cputcxy(byte x, byte y, char ch) {
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vrambuf_put(NTADR_A(x,y), &ch, 1);
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}
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void cputsxy(byte x, byte y, const char* str) {
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vrambuf_put(NTADR_A(x,y), str, strlen(str));
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}
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void clrscr() {
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vrambuf_clear();
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ppu_off();
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vram_adr(0x2000);
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vram_fill(0, 32*28);
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vram_adr(0x0);
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ppu_on_bg();
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}
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////////// GAME DATA
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typedef struct {
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byte x;
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byte y;
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byte dir;
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word score;
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char head_attr;
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char tail_attr;
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int collided:1;
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int human:1;
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} Player;
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Player players[2];
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byte attract;
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byte gameover;
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byte frames_per_move;
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#define START_SPEED 12
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#define MAX_SPEED 5
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#define MAX_SCORE 7
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///////////
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const char BOX_CHARS[8] = { '+','+','+','+','-','-','!','!' };
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void draw_box(byte x, byte y, byte x2, byte y2, const char* chars) {
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byte x1 = x;
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cputcxy(x, y, chars[2]);
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cputcxy(x2, y, chars[3]);
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cputcxy(x, y2, chars[0]);
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cputcxy(x2, y2, chars[1]);
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while (++x < x2) {
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cputcxy(x, y, chars[5]);
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cputcxy(x, y2, chars[4]);
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}
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while (++y < y2) {
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cputcxy(x1, y, chars[6]);
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cputcxy(x2, y, chars[7]);
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}
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}
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void draw_playfield() {
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draw_box(1,2,COLS-2,ROWS-1,BOX_CHARS);
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cputcxy(9,1,players[0].score+'0');
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cputcxy(28,1,players[1].score+'0');
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if (attract) {
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cputsxy(3,ROWS-1,"ATTRACT MODE - PRESS ENTER");
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} else {
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cputsxy(1,1,"PLYR1:");
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cputsxy(20,1,"PLYR2:");
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}
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}
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typedef enum { D_RIGHT, D_DOWN, D_LEFT, D_UP } dir_t;
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const char DIR_X[4] = { 1, 0, -1, 0 };
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const char DIR_Y[4] = { 0, 1, 0, -1 };
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void init_game() {
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memset(players, 0, sizeof(players));
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players[0].head_attr = '1';
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players[1].head_attr = '2';
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players[0].tail_attr = 0x06;
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players[1].tail_attr = 0x07;
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frames_per_move = START_SPEED;
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}
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void reset_players() {
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players[0].x = players[0].y = 5;
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players[0].dir = D_RIGHT;
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players[1].x = COLS-6;
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players[1].y = ROWS-6;
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players[1].dir = D_LEFT;
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players[0].collided = players[1].collided = 0;
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}
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void draw_player(Player* p) {
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cputcxy(p->x, p->y, p->head_attr);
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}
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void move_player(Player* p) {
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cputcxy(p->x, p->y, p->tail_attr);
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p->x += DIR_X[p->dir];
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p->y += DIR_Y[p->dir];
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if (getchar(p->x, p->y) != 0)
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p->collided = 1;
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draw_player(p);
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}
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void human_control(Player* p) {
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byte dir = 0xff;
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byte joy;
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joy = joy_read (JOY_1);
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// start game if attract mode
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if (attract && (joy & JOY_START_MASK))
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gameover = 1;
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// do not allow movement unless human player
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if (!p->human) return;
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if (joy & JOY_LEFT_MASK) dir = D_LEFT;
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if (joy & JOY_RIGHT_MASK) dir = D_RIGHT;
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if (joy & JOY_UP_MASK) dir = D_UP;
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if (joy & JOY_DOWN_MASK) dir = D_DOWN;
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// don't let the player reverse
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if (dir < 0x80 && dir != (p->dir ^ 2)) {
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p->dir = dir;
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}
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}
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byte ai_try_dir(Player* p, dir_t dir, byte shift) {
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byte x,y;
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dir &= 3;
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x = p->x + (DIR_X[dir] << shift);
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y = p->y + (DIR_Y[dir] << shift);
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if (x < COLS && y < ROWS && getchar(x, y) == 0) {
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p->dir = dir;
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return 1;
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} else {
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return 0;
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}
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}
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void ai_control(Player* p) {
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dir_t dir;
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if (p->human) return;
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dir = p->dir;
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if (!ai_try_dir(p, dir, 0)) {
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ai_try_dir(p, dir+1, 0);
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ai_try_dir(p, dir-1, 0);
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} else {
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ai_try_dir(p, dir-1, 0) && ai_try_dir(p, dir-1, 1+(rand() & 3));
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ai_try_dir(p, dir+1, 0) && ai_try_dir(p, dir+1, 1+(rand() & 3));
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ai_try_dir(p, dir, rand() & 3);
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}
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}
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void flash_colliders() {
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byte i;
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// flash players that collided
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for (i=0; i<56; i++) {
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//cv_set_frequency(CV_SOUNDCHANNEL_0, 1000+i*8);
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//cv_set_attenuation(CV_SOUNDCHANNEL_0, i/2);
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if (players[0].collided) players[0].head_attr ^= 0x80;
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if (players[1].collided) players[1].head_attr ^= 0x80;
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vrambuf_flush();
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vrambuf_flush();
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draw_player(&players[0]);
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draw_player(&players[1]);
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}
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//cv_set_attenuation(CV_SOUNDCHANNEL_0, 28);
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}
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void make_move() {
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byte i;
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for (i=0; i<frames_per_move; i++) {
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human_control(&players[0]);
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vrambuf_flush();
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}
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ai_control(&players[0]);
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ai_control(&players[1]);
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// if players collide, 2nd player gets the point
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move_player(&players[1]);
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move_player(&players[0]);
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}
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void declare_winner(byte winner) {
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byte i;
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clrscr();
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for (i=0; i<ROWS/2-3; i++) {
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draw_box(i,i,COLS-1-i,ROWS-1-i,BOX_CHARS);
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vrambuf_flush();
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}
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cputsxy(12,10,"WINNER:");
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cputsxy(12,13,"PLAYER ");
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cputcxy(12+7, 13, '1'+winner);
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vrambuf_flush();
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delay(75);
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gameover = 1;
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}
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#define AE(tl,tr,bl,br) (((tl)<<0)|((tr)<<2)|((bl)<<4)|((br)<<6))
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// this is attribute table data,
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// each 2 bits defines a color palette
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// for a 16x16 box
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const unsigned char Attrib_Table[0x40]={
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AE(3,3,1,0),AE(3,3,0,0),AE(3,3,0,0),AE(3,3,0,0), AE(2,2,0,0),AE(2,2,0,0),AE(2,2,0,0),AE(2,2,0,1),
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AE(1,0,1,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0), AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,1,0,1),
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AE(1,0,1,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0), AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,1,0,1),
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AE(1,0,1,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0), AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,1,0,1),
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AE(1,0,1,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0), AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,1,0,1),
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AE(1,0,1,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0), AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,1,0,1),
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AE(1,0,1,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0), AE(0,0,0,0),AE(0,0,0,0),AE(0,0,0,0),AE(0,1,0,1),
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AE(1,1,1,1),AE(1,1,1,1),AE(1,1,1,1),AE(1,1,1,1), AE(1,1,1,1),AE(1,1,1,1),AE(1,1,1,1),AE(1,1,1,1),
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};
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/*{pal:"nes",layout:"nes"}*/
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const unsigned char Palette_Table[16]={
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0x00,
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0x01,0x28,0x31,0x00,
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0x04,0x24,0x34,0x00,
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0x09,0x29,0x39,0x00,
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0x06,0x26,0x36
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};
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// put 8x8 grid of palette entries into the PPU
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void setup_attrib_table() {
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vram_adr(0x23c0);
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vram_write(Attrib_Table, 0x40);
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}
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void setup_palette() {
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int i;
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// only set palette entries 0-15 (background only)
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for (i=0; i<16; i++)
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pal_col(i, Palette_Table[i] ^ attract);
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}
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void play_round() {
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ppu_off();
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setup_attrib_table();
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setup_palette();
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clrscr();
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draw_playfield();
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reset_players();
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while (1) {
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make_move();
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if (gameover) return; // attract mode -> start
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if (players[0].collided || players[1].collided) break;
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}
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flash_colliders();
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// add scores to players that didn't collide
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if (players[0].collided) players[1].score++;
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if (players[1].collided) players[0].score++;
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// increase speed
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if (frames_per_move > MAX_SPEED) frames_per_move--;
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// game over?
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if (players[0].score != players[1].score) {
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if (players[0].score >= MAX_SCORE)
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declare_winner(0);
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else if (players[1].score >= MAX_SCORE)
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declare_winner(1);
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}
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}
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void play_game() {
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gameover = 0;
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init_game();
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if (!attract)
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players[0].human = 1;
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while (!gameover) {
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play_round();
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}
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}
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void main() {
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joy_install (joy_static_stddrv);
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vrambuf_clear();
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set_vram_update(updbuf);
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while (1) {
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attract = 1;
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play_game();
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attract = 0;
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play_game();
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}
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}
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