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feat: make space invaders playable

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This commit is contained in:
Stevan Freeborn
2026-07-18 08:28:24 -05:00
parent 87a6954ba1
commit e956e4abaa
2 changed files with 161 additions and 21 deletions
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main.c
+136 -6
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@@ -9,11 +9,31 @@
#define MEMORY_SIZE 4096
#define PROGRAM_START 512
#define FONT_START 80
#define CPU_CLOCK_HZ 600
#define TIMER_HZ 60
#define SCREEN_WIDTH 64
#define SCREEN_HEIGHT 32
const uint8_t fontset[80] = {
0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
0x20, 0x60, 0x20, 0x20, 0x70, // 1
0xF0, 0x10, 0xF0, 0x80, 0xF0, // 2
0xF0, 0x10, 0xF0, 0x10, 0xF0, // 3
0x90, 0x90, 0xF0, 0x10, 0x10, // 4
0xF0, 0x80, 0xF0, 0x10, 0xF0, // 5
0xF0, 0x80, 0xF0, 0x90, 0xF0, // 6
0xF0, 0x10, 0x20, 0x40, 0x40, // 7
0xF0, 0x90, 0xF0, 0x90, 0xF0, // 8
0xF0, 0x90, 0xF0, 0x10, 0xF0, // 9
0xF0, 0x90, 0xF0, 0x90, 0x90, // A
0xE0, 0x90, 0xE0, 0x90, 0xE0, // B
0xF0, 0x80, 0x80, 0x80, 0xF0, // C
0xE0, 0x90, 0x90, 0x90, 0xE0, // D
0xF0, 0x80, 0xF0, 0x80, 0xF0, // E
0xF0, 0x80, 0xF0, 0x80, 0x80 // F
};
const int CYCLES_PER_FRAME = CPU_CLOCK_HZ / TIMER_HZ;
volatile sig_atomic_t keep_running = 1;
@@ -43,6 +63,9 @@ typedef struct ChipEight {
uint16_t stack[16];
uint8_t sc;
uint32_t display[SCREEN_WIDTH * SCREEN_HEIGHT];
uint8_t keys[16];
uint8_t key_register;
bool waiting_for_key;
} chip_eight_t;
void println(const char *format, ...) {
@@ -84,7 +107,6 @@ void draw(chip_eight_t *chip) {
printf("\n");
}
}
void setup_graceful_exit() {
@@ -123,6 +145,12 @@ void init_chip(chip_eight_t *chip) {
chip->dt = 0;
chip->st = 0;
memset(chip->display, 0, sizeof(chip->display));
memset(chip->keys, 0, sizeof(chip->keys));
chip->waiting_for_key = false;
for (int i = 0; i < 80; i++) {
chip->memory[FONT_START + i] = fontset[i];
}
}
void draw_sprite(chip_eight_t *chip, uint16_t n, uint16_t x, uint16_t y) {
@@ -160,6 +188,28 @@ void draw_sprite(chip_eight_t *chip, uint16_t n, uint16_t x, uint16_t y) {
}
}
void update_keys(chip_eight_t *chip) {
chip->keys[1] = IsKeyDown(KEY_ONE);
chip->keys[2] = IsKeyDown(KEY_TWO);
chip->keys[3] = IsKeyDown(KEY_THREE);
chip->keys[12] = IsKeyDown(KEY_FOUR);
chip->keys[4] = IsKeyDown(KEY_Q);
chip->keys[5] = IsKeyDown(KEY_W);
chip->keys[6] = IsKeyDown(KEY_E);
chip->keys[13] = IsKeyDown(KEY_R);
chip->keys[7] = IsKeyDown(KEY_A);
chip->keys[8] = IsKeyDown(KEY_S);
chip->keys[9] = IsKeyDown(KEY_D);
chip->keys[14] = IsKeyDown(KEY_F);
chip->keys[10] = IsKeyDown(KEY_Z);
chip->keys[0] = IsKeyDown(KEY_X);
chip->keys[11] = IsKeyDown(KEY_C);
chip->keys[15] = IsKeyDown(KEY_V);
}
int main(int argc, char *argv[]) {
setup_graceful_exit();
@@ -181,6 +231,8 @@ int main(int argc, char *argv[]) {
int load_rom_result = load_rom(chip, argv[1]);
if (load_rom_result != 0) {
// TODO: Check for return value
// print helpful error message
return load_rom_result;
}
@@ -192,6 +244,40 @@ int main(int argc, char *argv[]) {
while(!WindowShouldClose() || !keep_running)
{
update_keys(chip);
if (chip->waiting_for_key) {
bool key_pressed = false;
for (int i = 0; i < 16; i++) {
if (chip->keys[i]) {
chip->V[chip->key_register] = i;
chip->waiting_for_key = false;
key_pressed = true;
break;
}
}
if (!key_pressed) {
BeginDrawing();
ClearBackground(BLACK);
for (int i = 0; i < SCREEN_HEIGHT; i++) {
for (int j = 0; j < SCREEN_WIDTH; j++) {
uint32_t screen_pixel = chip->display[i * SCREEN_WIDTH + j];
if (screen_pixel == 1) {
DrawRectangle(j * scale_factor, i * scale_factor, scale_factor, scale_factor, RAYWHITE);
}
}
}
EndDrawing();
continue;
}
}
for(int i = 0; i < CYCLES_PER_FRAME; i++) {
// read 2 bytes at a time from memory
// reading first 1 byte shifting left 1 byte ORing 2 byte
@@ -201,6 +287,9 @@ int main(int argc, char *argv[]) {
// extracting the lowest 12 bits of the instruction
uint16_t nnn = opcode & 4095;
//extracting the lowest 8 bits of the instruction
uint8_t nn = opcode & 255;
//extracting the lowest 4 bits of the instruction
uint16_t n = opcode & 15;
@@ -218,16 +307,16 @@ int main(int argc, char *argv[]) {
if (opcode == 224) { // 00E0
memset(chip->display, 0, sizeof(chip->display));
} else if (opcode == 238) { // 00EE
chip->pc = chip->stack[15];
chip->sc -= 1;
chip->pc = chip->stack[chip->sc];
}
break;
case 4096: // 1nnn
chip->pc = nnn;
break;
case 8192: // 2nnn
chip->stack[chip->sc] = chip->pc;
chip->sc += 1;
chip->stack[15] = chip->pc;
chip->pc = nnn;
break;
case 12288: // 3xkk
@@ -251,7 +340,7 @@ int main(int argc, char *argv[]) {
case 28672: // 7xkk
chip->V[x] += kk;
break;
case 32768:
case 32768: // 8xy0
// TODO: Maybe switch?
if (n == 0) {
chip->V[x] = chip->V[y];
@@ -281,6 +370,11 @@ int main(int argc, char *argv[]) {
chip->V[x] *= 2;
}
break;
case 36864: // 9xy0
if (chip->V[x] != chip->V[y]) {
chip->pc += 2;
}
break;
case 40960: // ANNN
chip->I = nnn;
break;
@@ -294,8 +388,44 @@ int main(int argc, char *argv[]) {
case 53248: // Dxyn
draw_sprite(chip, n, x, y);
break;
case 57502: // E09E
// TODO: Need to get key inputs
case 57344: // E000
if (nn == 158) {
if (chip->keys[chip->V[x]] == 1) {
chip->pc += 2;
}
} else if (nn == 161) {
if (chip->keys[chip->V[x]] != 1) {
chip->pc += 2;
}
}
break;
case 61440: // F000
if (nn == 7) {
chip->V[x] = chip->dt;
} else if (nn == 10) {
chip->waiting_for_key = true;
chip->key_register = x;
} else if (nn == 21) {
chip->dt = chip->V[x];
} else if (nn == 24) {
chip->st = chip->V[x];
} else if (nn == 30) {
chip->I += chip->V[x];
} else if (nn == 41) {
chip->I = FONT_START + (chip->V[x] * 5);
} else if (nn == 51) {
chip->memory[chip->I] = chip->V[x] / 100;
chip->memory[chip->I + 1] = (chip->V[x] / 10) % 10;
chip->memory[chip->I + 2] = chip->V[x] % 10;
} else if (nn == 85) {
for (int i = 0; i <= x; i++) {
chip->memory[chip->I + i] = chip->V[i];
}
} else if (nn == 101) {
for (int i = 0; i <= x; i++) {
chip->V[i] = chip->memory[chip->I + i];
}
}
break;
default:
break;