Python Raycaster

import pygame
#import math
from math import *
from pygame.locals import *

#PyRay 20x20
worldMap =  [
            [1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2],
            [2, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 2, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 2, 3, 2, 3, 0, 0, 2],
            [2, 0, 3, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2],
            [2, 3, 1, 0, 0, 2, 0, 0, 0, 2, 3, 2, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 2, 0, 0, 0, 2],
            [2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 2, 1, 0, 0, 0, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 3, 1, 0, 0, 0, 0, 0, 0, 0, 2],
            [2, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1],
            [1, 0, 2, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2],
            [2, 0, 3, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 3, 2, 1, 2, 0, 1],
            [1, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 0, 2],
            [2, 3, 1, 0, 0, 2, 0, 0, 2, 1, 3, 2, 0, 2, 0, 0, 3, 0, 3, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 1, 0, 0, 2, 0, 0, 2],
            [2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 3, 0, 1, 2, 0, 1],
            [1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 3, 0, 2],
            [2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 1],
            [2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1]]


mapSize = len(worldMap)

#Creates view window
pygame.init()
HEIGHT = 600
WIDTH = 1000
size = (WIDTH,HEIGHT)
screen = pygame.display.set_mode(size)
pygame.display.set_caption('Hmm')

keys = [False]*324 #List for keyboard values
zde = 0.0000001 #Add to prvent division by zero
res = 2


#Staring Position
xPos = 10.0
yPos = 5.0
xDir = -1
yDir = 0
xPlane = 0
yPlane = 0.66

rotationSpeed = 0.01
movementSpeed = 0.05


#Exits pygame
def close():
    pygame.display.quit()
    pygame.quit()

#Start game loop
while True:
    pygame.event.pump()

    #Draws background. Black and Grey
    screen.fill((25,25,25))
    pygame.draw.rect(screen, (50,50,50), (0, HEIGHT/2, WIDTH, HEIGHT/2)) #Draws grey rectangle in bottom half

    #Sets whether keys are held or not
    for event in pygame.event.get():
        if event.type == KEYDOWN:
            keys[event.key] = True
        elif event.type == KEYUP:
            keys[event.key] = False

    #Keybindings
    if keys[K_ESCAPE]:
        close()

    if keys[K_UP]:
        if not worldMap[int(xPos + xDir * movementSpeed)] [int(yPos)]:
            xPos += xDir * movementSpeed
        if not worldMap[int(xPos)][int(yPos + yDir * movementSpeed)]:
            yPos += yDir * movementSpeed

    if keys[K_DOWN]:
        if not worldMap[int(xPos - xDir * movementSpeed)] [int(yPos)]:
            xPos -= xDir * movementSpeed
        if not worldMap[int(xPos)][int(yPos - yDir * movementSpeed)]:
            yPos -= yDir * movementSpeed

    if keys[K_RIGHT]:
        xDirOld = xDir
        xDir = xDir * cos(-rotationSpeed) - yDir * sin(-rotationSpeed)
        yDir = xDirOld * sin(-rotationSpeed) + yDir * cos(-rotationSpeed)
        xPlaneOld = xPlane
        xPlane = xPlane * cos(-rotationSpeed) - yPlane * sin(-rotationSpeed)
        yPlane = xPlaneOld * sin(-rotationSpeed) + yPlane * cos(-rotationSpeed)

    if keys[K_LEFT]:
        xDirOld = xDir
        xDir = xDir * cos(rotationSpeed) - yDir * sin(rotationSpeed)
        yDir = xDirOld * sin(rotationSpeed) + yDir * cos(rotationSpeed)
        xPlaneOld = xPlane
        xPlane = xPlane * cos(rotationSpeed) - yPlane * sin(rotationSpeed)
        yPlane = xPlaneOld * sin(rotationSpeed) + yPlane * cos(rotationSpeed)




    for column in range(0,WIDTH,res):
        xCamera = 2 * column / float(WIDTH) - 1.0
        xRayDir = xDir + xPlane * xCamera
        yRayDir = yDir + yPlane * xCamera

        xMap = int(xPos)
        yMap = int(yPos)

        xSideDistance = 0.0
        ySideDistance = 0.0
        perpWallDistance = 0.0

        xDeltaDistance = abs(1/(xRayDir + zde))
        yDeltaDistance = abs(1/(yRayDir + zde))

        xStep = 0
        yStep = 0

        hit = False
        side = 0

        if (xRayDir < 0):
            xStep = -1
            xSideDistance = (xPos - xMap) * xDeltaDistance
        else:
            xStep = -1
            xSideDistance = (xMap + 1.0 - xPos) * xDeltaDistance

        if (xRayDir < 0):
            yStep = -1
            ySideDistance = (yPos - yMap) * yDeltaDistance
        else:
            yStep = 1;
            ySideDistance = (yMap + 1.0 - yPos) * yDeltaDistance

        hit = False
        while not hit:
            if (xSideDistance < ySideDistance):
              xSideDistance += xDeltaDistance
              xMap += xStep
              side = 'x'

            else:
              ySideDistance += yDeltaDistance
              yMap += yStep
              side = 'y'

            if worldMap[xMap][yMap] != 0 :
                hit = True

        if (side == 0):
            perpWallDist = (xMap - xPos + (1 - xStep) / 2) / (xRayDir + zde)
        else:
            perpWallDist = (yMap - yPos + (1 - yStep) / 2) / (yRayDir + zde)

        lineHeight = int(HEIGHT / (perpWallDist + zde))

        drawStart = -lineHeight / 2 + HEIGHT / 2

        if (drawStart < 0):
            drawStart = 0

        drawEnd = lineHeight / 2 + HEIGHT / 2

        if (drawEnd >= HEIGHT):
            drawEnd = HEIGHT - 1

        wallcolours = [ [255,255,255], [150,0,0], [0,150,0], [0,0,150] ]
        colour = wallcolours[worldMap[xMap][yMap]]

        if side == 'y':
            colour = [i/2 for i in colour]

        pygame.draw.line(screen, colour, (column,drawStart), (column, drawEnd), res)


    pygame.display.update() #Updates screen