Dotship: Juego en Arduino (LCD + Pot + Pushbutton)

/*
  __DOTSHIP__
  "The adventure of a dot-shaped ship versus the thing-shaped 
  immortal enemy"
 
  A simple Arduino game that uses a common 16x2 LCD (Hitachi 
  HD44780 compatible) and a potentiometer and a pushbutton as 
  a controller.
 
  You can find the LCD wiring here: 
  http://arduino.cc/en/Tutorial/LiquidCrystal
    - RS to 12
    - Enable to 11
    - Data pins to 5, 4, 3, 2
    - R/W to GND
 
  also you will need a:
  * Potentiometer: 
    - end pins to +5v and GND
    - middle pin to A0 pin
  * Pushbutton:
    - attached to pin 8 from +5V
    - 10K resistor attached to pin 8 from ground
 
  More details: http://thebatzuk.org/2011/09/dotship-juego-en-
  arduino-lcd-pot-pushbutton.html
 
  11 Sep 2011
  by Raúl Rivas (thebatzuk)   <--------\
                                        \  
  You can use, copy and modify           \
  this code but do not remove this  line -\
*/
 
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
 
unsigned long time = 0;
boolean game = true;
unsigned int score = 0;
 
// potentiometer and button pins
int pot_pin = 0;
int bttn_pin = 8;
int bttn_val = 0;
int bttn_last = 0;
 
// ship variables 
int ship_px = 0;
int ship_y = 0;
 
// shoots variables
boolean shot = false;
int shoot_time = 0;
byte shot_pos[5] = {B00001, B00010, B00100, B01000, B10000};
int shoot_x = 14;
int shoot_y = 0;
int shoot_px = 0;
int mi = 0;
 
// enemies variables
byte enemies[8] = {B00000, B00110, B00001, B01111, B01111, 
                   B00001, B00110, B00000};
int enemy_y = 0;
int enemy_x = 0;
int enemy_vel = 100;
int vel_increment = 20;
 
void setup() 
{
  lcd.begin(16, 2);
  lcd.createChar(2, enemies);
  randomSeed(analogRead(1));
}
 
void loop() 
{
  if(game)
  {
    time++;
    // ship stuff
    byte ship[8] = {B00000, B00000, B00000, B00000, B00000, 
                    B00000, B00000, B00000};
    ship_px = map(analogRead(pot_pin), 0, 1023, 0, 16);
    if(ship_px >= 0 && ship_px <= 7)
      ship_y = 0;
    else if(ship_px >= 8 && ship_px <= 15)
      ship_y = 1; 
    ship[ship_px - ship_y * 8] = B10000;
    lcd.createChar(0, ship);
    lcd.setCursor(15, ship_y);
    lcd.write(0);
 
    // shoots stuff
    byte shoot[8] = {B00000, B00000, B00000, B00000, B00000, 
                     B00000, B00000, B00000};
    bttn_val = digitalRead(bttn_pin);
    if(bttn_val != bttn_last && bttn_val == HIGH && !shot)
    {
      shot = true;
      shoot_time = 0;
      mi = 0;
      shoot_px = ship_px - ship_y * 8;
      shoot_y = ship_y;
    }
    if(shot)
    {
      for(int i = 0; i < 15; i++)
      {
        if(shoot_time >= mi && shoot_time <= mi+4)
        {
          shoot_x = 14 - (mi / 5);
          mi += 5;
          if(shoot_x == 0)
            shot = false;
          break;
        }
      }
      shoot[shoot_px] = shot_pos[shoot_time - (14 - shoot_x) * 5];
      lcd.createChar(1, shoot);
      lcd.setCursor(shoot_x, shoot_y);
      lcd.write(1);
      shoot_time++;
    }
 
    // enemies stuff
    if(time % enemy_vel == 0)
    {
      enemy_x++;
      enemy_y = random(0, 2);
    }
    lcd.setCursor(enemy_x, enemy_y);
    lcd.write(2);
    // enemy got shot:
    if(shoot_y == enemy_y && shoot_x == enemy_x && 
       shoot_px > 0 && shoot_px < 7)
    {
      score += 10 * enemy_x;
      enemy_x = 0;
      enemy_vel -= vel_increment;
      vel_increment -= 5;
      if(enemy_vel <= 0)
        enemy_vel = 2;
      if(vel_increment <= 0)
        vel_increment = 5;
      shot = false;
      shoot_x = 14;
      delay(25);
    }
    else if(enemy_x > 14)
      game = false;
 
    // other stuff
    delay(15);
    lcd.clear();
    bttn_last = bttn_val;
  }
  else
  { 
    lcd.setCursor(0, 0); 
    lcd.print("Game Over.");
    lcd.setCursor(0, 1); 
    lcd.print("Score: ");
    lcd.print(score);
    // reset Arduino to play again
  }
}