// SPACE INVADERS V4
// XIAO RP2040 + SSD1306 OLED + touch pads
// Updated with centered title, intro art, denser/higher invaders,
// level complete screen, game over rules, and improved sprite shapes.
#include <Arduino.h>
#include <U8g2lib.h>
#include <Wire.h>
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);
static const uint8_t PIN_LEFT = D1;
static const uint8_t PIN_RIGHT = D7;
static const uint8_t PIN_A = D9;
static const uint8_t PIN_B = D10;
#define N_TOUCH 4
#define THRESHOLD 6
int touch_pins[N_TOUCH] = { PIN_LEFT, PIN_RIGHT, PIN_A, PIN_B };
bool nowT[N_TOUCH] = {false, false, false, false};
bool pastT[N_TOUCH] = {false, false, false, false};
void update_touch() {
  for (int i = 0; i < N_TOUCH; i++) {
    int p = touch_pins[i];
    pinMode(p, OUTPUT);
    digitalWrite(p, LOW);
    delayMicroseconds(20);
    pinMode(p, INPUT_PULLUP);
    int t = 0;
    while (!digitalRead(p) && t < 200) t++;
    pastT[i] = nowT[i];
    nowT[i] = (t > THRESHOLD);
  }
}
bool pressed(int i) { return nowT[i] && !pastT[i]; }
bool held(int i) { return nowT[i]; }
enum { T_LEFT = 0, T_RIGHT = 1, T_A = 2, T_B = 3 };
// ================= GAME CONSTANTS =================
#define EC 5
#define ER 3
#define MAX_BULLETS 4
const int PLAYER_Y = 58;
const int PLAYER_W = 12;
const int ENEMY_W = 10;
const int ENEMY_H = 8;
const int ENEMY_GAP_X = 5;
const int ENEMY_GAP_Y = 4;   // denser vertically
const int ENEMY_START_X = 18;
const int ENEMY_START_Y = 10; // higher
// ================= GAME STATE =================
int px = 58;
int level = 1;
int ex = ENEMY_START_X;
int ey = ENEMY_START_Y;
int dir = 1;
int enemyStepDelay = 22;
int enemyFrame = 0;
unsigned long lastEnemyMove = 0;
bool enemy[ER][EC];
bool intro = true;
bool gameOver = false;
bool levelComplete = false;
int completedLevel = 1;
unsigned long introTick = 0;
struct Bullet {
  int x;
  int y;
  bool a;
};
Bullet bullets[MAX_BULLETS];
// ================= HELPERS =================
void clearBullets() {
  for (int i = 0; i < MAX_BULLETS; i++) bullets[i].a = false;
}
void initEnemies() {
  for (int r = 0; r < ER; r++) {
    for (int c = 0; c < EC; c++) {
      enemy[r][c] = true;
    }
  }
  ex = ENEMY_START_X;
  ey = ENEMY_START_Y;
  dir = 1;
  clearBullets();
}
bool enemiesAlive() {
  for (int r = 0; r < ER; r++) {
    for (int c = 0; c < EC; c++) {
      if (enemy[r][c]) return true;
    }
  }
  return false;
}
void startGame() {
  level = 1;
  px = 58;
  gameOver = false;
  levelComplete = false;
  initEnemies();
}
void startNextLevel() {
  level++;
  if (level > 3) level = 1;
  levelComplete = false;
  px = 58;
  initEnemies();
}
// ================= PLAYER =================
void drawPlayer() {
  // more interesting ship shape
  u8g2.drawPixel(px + 5, PLAYER_Y - 3);
  u8g2.drawBox(px + 4, PLAYER_Y - 2, 3, 1);
  u8g2.drawBox(px + 3, PLAYER_Y - 1, 5, 1);
  u8g2.drawBox(px + 2, PLAYER_Y, 7, 1);
  u8g2.drawBox(px + 1, PLAYER_Y + 1, 9, 1);
  u8g2.drawBox(px, PLAYER_Y + 2, 12, 1);
  u8g2.drawPixel(px + 1, PLAYER_Y + 3);
  u8g2.drawPixel(px + 10, PLAYER_Y + 3);
}
// ================= BULLETS =================
void fire() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].a) {
      bullets[i].x = px + PLAYER_W / 2;
      bullets[i].y = PLAYER_Y - 5;
      bullets[i].a = true;
      break;
    }
  }
}
void updateBullets() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (bullets[i].a) {
      bullets[i].y -= 3;
      if (bullets[i].y < 0) bullets[i].a = false;
    }
  }
}
void drawBullets() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (bullets[i].a) u8g2.drawVLine(bullets[i].x, bullets[i].y, 3);
  }
}
// ================= ENEMIES =================
void drawEnemyType1(int x, int y, bool phase) {
  u8g2.drawBox(x + 2, y, 6, 1);
  u8g2.drawBox(x + 1, y + 1, 8, 1);
  u8g2.drawBox(x, y + 2, 10, 1);
  u8g2.drawPixel(x + 2, y + 3);
  u8g2.drawPixel(x + 7, y + 3);
  if (phase) {
    u8g2.drawLine(x + 1, y + 4, x + 3, y + 6);
    u8g2.drawLine(x + 8, y + 4, x + 6, y + 6);
  } else {
    u8g2.drawLine(x + 2, y + 4, x + 1, y + 6);
    u8g2.drawLine(x + 7, y + 4, x + 8, y + 6);
  }
}
void drawEnemyType2(int x, int y, bool phase) {
  u8g2.drawFrame(x + 1, y + 1, 8, 4);
  u8g2.drawPixel(x, y + 2);
  u8g2.drawPixel(x + 9, y + 2);
  u8g2.drawPixel(x + 3, y + 2);
  u8g2.drawPixel(x + 6, y + 2);
  if (phase) {
    u8g2.drawLine(x + 2, y + 5, x + 1, y + 6);
    u8g2.drawLine(x + 7, y + 5, x + 8, y + 6);
  } else {
    u8g2.drawLine(x + 3, y + 5, x + 3, y + 6);
    u8g2.drawLine(x + 6, y + 5, x + 6, y + 6);
  }
}
void drawEnemyType3(int x, int y, bool phase) {
  u8g2.drawPixel(x + 4, y);
  u8g2.drawBox(x + 2, y + 1, 5, 1);
  u8g2.drawBox(x + 1, y + 2, 7, 1);
  u8g2.drawBox(x, y + 3, 9, 1);
  u8g2.drawPixel(x + 2, y + 4);
  u8g2.drawPixel(x + 6, y + 4);
  if (phase) {
    u8g2.drawLine(x + 2, y + 5, x + 1, y + 6);
    u8g2.drawLine(x + 6, y + 5, x + 7, y + 6);
  } else {
    u8g2.drawLine(x + 3, y + 5, x + 3, y + 6);
    u8g2.drawLine(x + 5, y + 5, x + 5, y + 6);
  }
}
void drawEnemy(int x, int y, int rowType) {
  bool phase = ((millis() / 220) % 2) == 0;
  if (level == 1) {
    drawEnemyType1(x, y, phase);
  } else if (level == 2) {
    drawEnemyType2(x, y, phase);
  } else {
    // mix on level 3
    if (rowType == 0) drawEnemyType1(x, y, phase);
    else if (rowType == 1) drawEnemyType2(x, y, phase);
    else drawEnemyType3(x, y, phase);
  }
}
void drawEnemies() {
  for (int r = 0; r < ER; r++) {
    for (int c = 0; c < EC; c++) {
      if (enemy[r][c]) {
        int x = ex + c * (ENEMY_W + ENEMY_GAP_X);
        int y = ey + r * (ENEMY_H + ENEMY_GAP_Y);
        drawEnemy(x, y, r);
      }
    }
  }
}
void updateEnemies() {
  if (millis() - lastEnemyMove < (unsigned long)enemyStepDelay) return;
  lastEnemyMove = millis();
  enemyFrame++;
  int speed = level;
  ex += dir * speed;
  // Find bounds using only alive invaders
  int leftMost = 999;
  int rightMost = -999;
  int bottomMost = -999;
  for (int r = 0; r < ER; r++) {
    for (int c = 0; c < EC; c++) {
      if (!enemy[r][c]) continue;
      int x = ex + c * (ENEMY_W + ENEMY_GAP_X);
      int y = ey + r * (ENEMY_H + ENEMY_GAP_Y);
      if (x < leftMost) leftMost = x;
      if (x + ENEMY_W > rightMost) rightMost = x + ENEMY_W;
      if (y + ENEMY_H > bottomMost) bottomMost = y + ENEMY_H;
    }
  }
  if (leftMost == 999) return; // no alive invaders
  if (leftMost < 2 || rightMost > 126) {
    dir = -dir;
    ex += dir * speed;
    ey += 3;
    // recompute bottom after stepping down
    bottomMost = -999;
    for (int r = 0; r < ER; r++) {
      for (int c = 0; c < EC; c++) {
        if (!enemy[r][c]) continue;
        int y = ey + r * (ENEMY_H + ENEMY_GAP_Y);
        if (y + ENEMY_H > bottomMost) bottomMost = y + ENEMY_H;
      }
    }
  }
  // Game over only if a STILL-ALIVE invader reaches the base height
  if (bottomMost >= PLAYER_Y - 2) {
    gameOver = true;
  }
  // Game over only if a STILL-ALIVE invader touches the player area
  for (int r = 0; r < ER; r++) {
    for (int c = 0; c < EC; c++) {
      if (!enemy[r][c]) continue;
      int x = ex + c * (ENEMY_W + ENEMY_GAP_X);
      int y = ey + r * (ENEMY_H + ENEMY_GAP_Y);
      bool hitPlayerZone = !(x + ENEMY_W < px || x > px + PLAYER_W ||
y + ENEMY_H < PLAYER_Y - 4 || y > PLAYER_Y + 3);
      if (hitPlayerZone) {
        gameOver = true;
      }
    }
  }
}
// ================= COLLISION =================
void checkHit() {
  for (int i = 0; i < MAX_BULLETS; i++) {
    if (!bullets[i].a) continue;
    for (int r = 0; r < ER; r++) {
      for (int c = 0; c < EC; c++) {
        if (!enemy[r][c]) continue;
        int x = ex + c * (ENEMY_W + ENEMY_GAP_X);
        int y = ey + r * (ENEMY_H + ENEMY_GAP_Y);
        if (bullets[i].x > x && bullets[i].x < x + ENEMY_W &&
bullets[i].y > y && bullets[i].y < y + ENEMY_H) {
          enemy[r][c] = false;
          bullets[i].a = false;
        }
      }
    }
  }
}
// ================= INTRO =================
void drawMonsterHead3D(int x, int y, int frame) {
  // pseudo-3D face on right side
  u8g2.drawRFrame(x, y, 28, 20, 3);
  u8g2.drawRFrame(x + 2, y + 2, 24, 16, 2);
  u8g2.drawDisc(x + 8, y + 8, 2, U8G2_DRAW_ALL);
  u8g2.drawDisc(x + 20, y + 8, 2, U8G2_DRAW_ALL);
  u8g2.drawLine(x + 6, y + 14, x + 22, y + 14);
  u8g2.drawLine(x + 3, y + 3, x - 2, y - 2);
  u8g2.drawLine(x + 25, y + 3, x + 30, y - 2);
  if (frame % 20 < 10) {
    u8g2.drawLine(x + 10, y + 15, x + 14, y + 17);
    u8g2.drawLine(x + 18, y + 15, x + 14, y + 17);
  } else {
    u8g2.drawLine(x + 9, y + 16, x + 19, y + 16);
  }
}
void drawIntro() {
  u8g2.clearBuffer();
  int frame = (millis() / 90) % 40;
  // left side text
  u8g2.setFont(u8g2_font_7x13B_tr);
  u8g2.drawStr(8, 14, "SPACE");
  u8g2.drawStr(8, 28, "INVADERS");
  u8g2.setFont(u8g2_font_5x8_tf);
  u8g2.drawStr(8, 39, "by Yaro");
  // right side monster face
  drawMonsterHead3D(88, 8, frame);
  // small battle scene lower area
  int invX = 16 + (frame % 18);
  drawEnemyType3(invX, 46, frame % 2 == 0);
  drawEnemyType2(invX + 18, 46, frame % 2 != 0);
  drawPlayer();
  if (frame % 16 < 8) {
    u8g2.drawVLine(px + 6, 44, 8);
  }
  u8g2.drawHLine(0, 54, 128);
  u8g2.setFont(u8g2_font_6x12_tr);
  u8g2.drawStr(28, 63, "PRESS B");
  u8g2.sendBuffer();
}
// ================= SCREENS =================
void drawHUD() {
  u8g2.setFont(u8g2_font_5x8_tf);
  u8g2.setCursor(0, 8);
  u8g2.print("LVL:");
  u8g2.print(level);
}
void drawLevelComplete() {
  u8g2.clearBuffer();
  u8g2.setFont(u8g2_font_6x12_tr);
  u8g2.drawStr(14, 20, "LEVEL COMPLETE");
  u8g2.setFont(u8g2_font_5x8_tf);
  u8g2.drawStr(22, 34, "Press B for the");
  u8g2.drawStr(32, 44, "next level");
  u8g2.drawStr(48, 56, "L=");
  u8g2.print(completedLevel);
  u8g2.sendBuffer();
}
void drawGameOver() {
  u8g2.clearBuffer();
  u8g2.setFont(u8g2_font_7x13B_tr);
  u8g2.drawStr(22, 22, "GAME OVER");
  u8g2.setFont(u8g2_font_5x8_tf);
  u8g2.drawStr(18, 38, "Invaders reached");
  u8g2.drawStr(35, 46, "the base");
  u8g2.drawStr(18, 58, "Press B to restart");
  u8g2.sendBuffer();
}
void render() {
  u8g2.clearBuffer();
  drawHUD();
  drawEnemies();
  drawBullets();
  drawPlayer();
  u8g2.sendBuffer();
}
// ================= SETUP =================
void setup() {
  Serial.begin(115200);
  Wire.begin();
  u8g2.begin();
  startGame();
}
// ================= LOOP =================
void loop() {
  update_touch();
  if (intro) {
    drawIntro();
    if (pressed(T_B)) {
      intro = false;
      startGame();
    }
    delay(30);
    return;
  }
  if (gameOver) {
    drawGameOver();
    if (pressed(T_B)) {
      startGame();
    }
    delay(30);
    return;
  }
  if (levelComplete) {
    drawLevelComplete();
    if (pressed(T_B)) {
      startNextLevel();
    }
    delay(30);
    return;
  }
  if (held(T_LEFT)) px -= 2;
  if (held(T_RIGHT)) px += 2;
  if (px < 0) px = 0;
  if (px > 116) px = 116;
  if (pressed(T_A)) fire();
  updateBullets();
  updateEnemies();
  checkHit();
  if (!enemiesAlive()) {
    completedLevel = level;
    levelComplete = true;
  }
  render();
  delay(30);
}