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#include <pic16f84a.h>
typedef unsigned char uint8_t;
/* Mapped for emulator/simulator environment */
__sfr __at(0x70) UART_TX;
__sfr __at(0x71) UART_RX;
__sfr __at(0x72) UART_STATUS;
#define GRID_W 20
#define GRID_H 10
#define MAX_LEN 10
#define OVF_PER_FRAME 20
#define DIR_UP 0
#define DIR_DOWN 1
#define DIR_LEFT 2
#define DIR_RIGHT 3
static __near uint8_t snake_x[MAX_LEN];
static __near uint8_t snake_y[MAX_LEN];
static __near uint8_t snake_len;
static __near uint8_t direction;
static __near uint8_t last_moved_dir;
static __near uint8_t food_x;
static __near uint8_t food_y;
static __near uint8_t score;
static volatile __near uint8_t ovf_count;
void isr(void) __interrupt(0) {
if (INTCON & 0x04) {
ovf_count++;
INTCON &= ~(uint8_t)0x04;
}
}
static uint8_t r_seed = 0xAA; // Seed must NEVER be 0
static uint8_t get_random(void) {
// Standard 8-bit LFSR logic (similar to your assembly)
// If the LSB is 1, XOR with the polynomial mask
if (r_seed & 1) {
r_seed = (r_seed >> 1) ^ 0xB8;
} else {
r_seed = (r_seed >> 1);
}
return r_seed;
}
static void uart_send(uint8_t b) {
while (UART_STATUS & 0x01);
UART_TX = b;
}
static void uart_puts(const char *s) {
while (*s) uart_send((uint8_t)*s++);
}
static uint8_t uart_recv(void) {
if (UART_STATUS & 0b00000010) return 0;
return UART_RX;
}
/* Simplified WASD handler */
static void handle_input(void) {
uint8_t c;
while (!(UART_STATUS & 0x02)) {
c = UART_RX;
/* Handle both upper and lower case */
if (c == 'w' || c == 'W') {
if (last_moved_dir != DIR_DOWN) direction = DIR_UP;
} else if (c == 's' || c == 'S') {
if (last_moved_dir != DIR_UP) direction = DIR_DOWN;
} else if (c == 'a' || c == 'A') {
if (last_moved_dir != DIR_RIGHT) direction = DIR_LEFT;
} else if (c == 'd' || c == 'D') {
if (last_moved_dir != DIR_LEFT) direction = DIR_RIGHT;
}
}
}
static void place_food(void) {
uint8_t x, y, i, overlap;
do {
overlap = 0;
// Get a random X and Y using the PRNG
x = get_random();
while (x >= GRID_W) x -= GRID_W;
y = get_random();
while (y >= GRID_H) y -= GRID_H;
/* Ensure food doesn't spawn inside the snake's body */
for (i = 0; i < snake_len; i++) {
if (snake_x[i] == x && snake_y[i] == y) {
overlap = 1;
break;
}
}
} while (overlap);
food_x = x;
food_y = y;
}
static void print_uint8(uint8_t v) {
uint8_t started = 0;
if (v >= 200) { uart_send('2'); v -= 200; started = 1; }
else if (v >= 100) { uart_send('1'); v -= 100; started = 1; }
{
uint8_t t = '0';
while (v >= 10) { v -= 10; t++; }
if (started || t != '0') uart_send(t);
}
uart_send(v + '0');
}
uint8_t food_ch = '*';
static void render(void) {
uint8_t x, y, i;
uart_puts("\x1B[H"); /* Cursor to home */
uart_send('+');
for (x = 0; x < GRID_W; x++) uart_send('-');
uart_puts("+\r\n");
for (y = 0; y < GRID_H; y++) {
uart_send('|');
for (x = 0; x < GRID_W; x++) {
uint8_t ch = ' ';
if (x == food_x && y == food_y) ch = food_ch;
else {
for (i = 0; i < snake_len; i++) {
if (snake_x[i] == x && snake_y[i] == y) {
ch = (i == 0) ? 'O' : 'o';
break;
}
}
}
uart_send(ch);
}
uart_puts("|\r\n");
}
uart_send('+');
for (x = 0; x < GRID_W; x++) uart_send('-');
uart_puts("+\r\nScore: ");
print_uint8(score);
uart_puts(" \r\n");
}
static uint8_t update(void) {
uint8_t nx, ny, i;
last_moved_dir = direction;
nx = snake_x[0]; ny = snake_y[0];
switch (direction) {
case DIR_UP: if (ny == 0) return 0; ny--; break;
case DIR_DOWN: if (ny == GRID_H-1) return 0; ny++; break;
case DIR_LEFT: if (nx == 0) return 0; nx--; break;
case DIR_RIGHT: if (nx == GRID_W-1) return 0; nx++; break;
}
for (i = 0; i < snake_len - 1; i++) {
if (snake_x[i] == nx && snake_y[i] == ny) return 0;
}
if (nx == food_x && ny == food_y) {
if (snake_len < MAX_LEN) snake_len++;
score++;
place_food();
}
for (i = snake_len - 1; i > 0; i--) {
snake_x[i] = snake_x[i-1];
snake_y[i] = snake_y[i-1];
}
snake_x[0] = nx; snake_y[0] = ny;
return 1;
}
void main(void) {
uint8_t alive;
TRISA &= ~0x01;
PORTA = 0x00;
OPTION_REG = 0x07;
TMR0 = 0;
INTCON = 0xa0;
while (1) {
direction = DIR_RIGHT;
last_moved_dir = DIR_RIGHT;
snake_len = 3;
score = 0;
snake_x[0] = 5; snake_y[0] = 5;
snake_x[1] = 4; snake_y[1] = 5;
snake_x[2] = 3; snake_y[2] = 5;
place_food();
/* \x1B[2J = Clear Screen
\x1B[H = Home Cursor
\x1B[?25l = Hide Cursor */
uart_puts("\x1B[2J\x1B[H\x1B[?25l");
alive = 1;
while (alive) {
/* High-frequency input polling during wait */
while (ovf_count < OVF_PER_FRAME) {
handle_input();
}
ovf_count = 0;
if (food_ch == '*')
food_ch = '+';
else
food_ch = '*';
alive = update();
render();
PORTA ^= 0x01;
}
/* Game Over: Show Cursor (\x1B[?25h) */
uart_puts("\r\n--- GAME OVER ---\r\nScore: ");
print_uint8(score);
uart_puts("\r\nPress any key to restart\r\n\x1B[?25h");
while (uart_recv() == 0);
}
}
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