#Space Inavders - Part
#Set up the screen
#Python 2.7
import turtle
import os
import math


#Set up the screen
wn = turtle.Screen()
wn.bgcolor("black")
wn.title("Space Invaders")

#Draw border
border_pen = turtle.Turtle()
border_pen.speed(0)
border_pen.color("White")
border_pen.penup()
border_pen.setposition(-300,-300)
border_pen.pendown()
border_pen.pensize(3)
for side in range(4):
    border_pen.forward(600)
    border_pen.left(90)
border_pen.hideturtle()

#Create the player turtle
player = turtle.Turtle()
player.color("blue")
player.shape("triangle")
player.penup()
player.speed(0)
player.setposition(0, -250)
player.setheading(90)

playerspeed = 15

#Create the enemy
enemy = turtle.Turtle()
enemy.color("red")
enemy.shape("circle")
enemy.penup()
enemy.speed(0)
enemy.setposition(-200, 250)

enemyspeed = 2

#Create the player's bullet
bullet = turtle.Turtle()
bullet.color("yellow")
bullet.shape("triangle")
bullet.penup()
bullet.speed(0)
bullet.setheading(90)
bullet.shapesize(0.5, 0.5)
bullet.hideturtle()

bulletspeed = 20

#Define bullet state
#ready - ready to fire
#fire - bullet is firing
bulletstate = "ready"

#Move the player left and right
def move_left():
    x = player.xcor()
    x -= playerspeed
    if x < -280:
        x =  280
    player.setx(x)

def move_right():
    x = player.xcor()
    x += playerspeed
    if x > 280:
        x = - 280
    player.setx(x)

def fire_bullet():
    #Declare bulletstate as a global if it needs changed
    global bulletstate
    if bulletstate == "ready":
        bulletstate = "fire"
        #Move the bullet to just above the player
        x = player.xcor()
        y = player.ycor()
        bullet.setposition(x, y + 10)
        bullet.showturtle()

def isCollision(t1, t2):
    distance = math.sqrt(math.pow(t1.xcor()-t2.xcor(),2))+(math.pow(t1.ycor()-t2.ycor(),2))
    if distance < 10:
        return True
    else:
        return False



#Create keyboard bindings
turtle.listen()
turtle.onkey(move_left, "Left")
turtle.onkey(move_right, "Right")
turtle.onkey(fire_bullet, "space")

#Main game loop
while True:

    #Move the enemy
    x = enemy.xcor()
    x += enemyspeed
    enemy.setx(x)

    #Move the enemy back and down
    if enemy.xcor() > 280:
        y = enemy.ycor()
        y -= 40
        enemyspeed *= -1
        enemy.sety(y)


    if enemy.xcor () < -280:
        y = enemy.ycor()
        y -= 40
        enemyspeed *= -1
        enemy.sety(y)

    #Move the bullet
    if bulletstate == "fire":
        y = bullet.ycor()
        y += bulletspeed
        bullet.sety(y)

    #Check to see if the bullet has gone to the top
    if bullet.ycor() > 275:
        bullet.hideturtle()
        bulletstate = "ready"

    #Check if the enemy and the bullet collide
    if isCollision(bullet, enemy):
        #Reset the bullet
        bullet.hideturtle()
        bulletstate = "ready"
        bullet.setposition(0, -400)
        #Reset the enemy
        enemy.setposition(-200, 250)
















delay = turtle.done()