Got unfair grade on exam, where do i go from here?

This isn't "superadvanced" by any means, but for a sorta beginners course of flash i'd say its pretty good, at least a C, but please tell me waht u think. THis is the main class btw, other classes are enemyFire/Ice/Earth etc and weapontypes, thePlayer, MySound and one more which i cant remember(lol tired).


package // Main code/class
{

import flash.display.*;
import flash.events.*;
import flash.ui.Keyboard;
import flash.text.TextField;
import flash.media.Sound;
import flash.net.URLRequest;
import flash.events.MouseEvent;
import flash.utils.Timer;
import flash.events.TimerEvent;

public class main extends MovieClip
{
private var player:thePlayer;
private var enemyTime:int = 0;
private var enemyLimit:int = 100;
private var myHitsNo:int;
private var mybullets:Array;
private var enemys:Array;
private var weaponType:int;
private var myLives:int;
private var fireTimer:Timer; //delay between shots
private var canFire:Boolean = true;
private var mySound:MySound;
private var bulletSpeed:Number = -450;

//public var soundFX = new Sound();
public var spawnPoint1:int = 295;
public var spawnPoint2:int = 385;
public var spawnPoint3:int = 475;
public var spawnPoint4:int = 567;;
public var enemySpeed:int = 4;

public function main()
{
//load sounds
mySound = new MySound();
}

private function playGame(event:MouseEvent)
{
gotoAndStop(2);
// initialize
myLives = 5;
myHitsNo = 0;
weaponType = 1;
mybullets = new Array();
enemys = new Array();
myScoreTxt.text = "Score: " + myHitsNo;
myLivesTxt.text = "Lives: " + myLives;

fireTimer = new Timer(400, 1);
fireTimer.addEventListener(TimerEvent.TIMER, shootTimerHandler, false, 0, true);

stage.addEventListener(KeyboardEvent.KEY_DOWN, listenKeyDown);
stage.addEventListener(Event.ENTER_FRAME, addEnemy);
stage.addEventListener(Event.ENTER_FRAME, checkCollision);
player = new thePlayer(stage.stageWidth-40, spawnPoint2);// stage.stageHeight/2);
stage.focus = player;
addChild(player);

mySound.playBgSound();
}

private function cleanUp()
{
stage.removeEventListener(KeyboardEvent.KEY_DOWN, listenKeyDown);
stage.removeEventListener(Event.ENTER_FRAME, addEnemy);
stage.removeEventListener(Event.ENTER_FRAME, checkCollision);

// remove all children manually
// copy the array so we dont delete items in the array
// we`re working in
var tmpArray = new Array();
for(var i in mybullets)
{
tmpArray.push(mybullets[i]);
}
for (var j in tmpArray)
{
tmpArray[j].deleteBullet();
}

tmpArray = new Array();
for(var k in enemys)
{
tmpArray.push(enemys[k]);
}
for(var l in tmpArray)
{
tmpArray[l].deleteEnemy();
}

removeChild(player);
fireTimer = null;

mySound.stopBgSound();
}

private function gotoStartScreen(event:MouseEvent)
{
cleanUp();
gotoAndStop(1);
}

public function listenKeyDown(event:KeyboardEvent) // Controls and weapontype selector
{
if (event.keyCode == 37) //left
{
player.movethePlayerDown();
}
if (event.keyCode == 39) //right
{
player.movethePlayerUp();
}
if (event.keyCode == Keyboard.SPACE) //space
{
shootBullet();
//soundFX.attachSound("Pistol Fire.wav");
//soundFX.start();
}
if (event.keyCode == Keyboard.NUMBER_1)
{
weaponType = 1;
}
if (event.keyCode == Keyboard.NUMBER_2)
{
weaponType = 2;
}
if (event.keyCode == Keyboard.NUMBER_3)
{
weaponType = 3;
}
if (event.keyCode == Keyboard.NUMBER_4)
{
weaponType = 4;
}
}

public function shootBullet() // Self explanatory, shoots the bullet and which type of bullet
{
if (canFire)
{
if(weaponType == 1) // fire
{
mySound.playFireSound();
var b:shotFire = new shotFire(player.x,player.y, bulletSpeed);
addChild(b);
mybullets.push(b);
}
if(weaponType == 2) // water
{
mySound.playWaterSound();
var c:shotWater = new shotWater(player.x,player.y, bulletSpeed);
addChild(c);
mybullets.push(c);
}
if(weaponType == 3) // light
{
mySound.playLightSound();
var d:shotLight = new shotLight(player.x,player.y, bulletSpeed);
addChild(d);
mybullets.push(d);
}
if(weaponType == 4) // earth
{
mySound.playEarthSound();
var e:shotEarth = new shotEarth(player.x,player.y, bulletSpeed);
addChild(e);
mybullets.push(e);
}
canFire = false;
fireTimer.start();
}
}

private function shootTimerHandler(e:TimerEvent) : void
{
//timer ran, we can shoot again.
canFire = true;
}

public function removeBullet(mybullet) // Removes bullet
{
for(var i in mybullets)
{
if (mybullets[i] == mybullet)
{
mybullets.splice(i,1);
break;
}
}
}

public function removeEnemy(myEnemy) // Removes enemies
{
for(var i in enemys)
{
if (enemys[i] == myEnemy)
{
enemys.splice(i,1);
break;
}
}
}

// returns true if im out of lives; dead
public function decreaseLivesAndCheckIfDead() : Boolean // decreases lives with 1 and updates the status text
{
myLives--;
myLivesTxt.text = "Lives: " + myLives;
if (myLives < 0)
{
var score = myHitsNo; // save the score before cleanUp()
cleanUp();
gotoAndStop(3); // go to the game over screen
finalScoreTxt.text = "Your score: " + score;
return true;
}
return false;
}

public function checkCollision(event:Event) // Collision detection, but also block speed increase,
{
// copy the arrays so we dont delete items in our working arrays
var tmpArrayEnemys = new Array();
for (var k in enemys)
{
tmpArrayEnemys.push(enemys[k]);
}
var tmpArrayBullets = new Array();
for (var l in mybullets)
{
tmpArrayBullets.push(mybullets[l]);
}

for(var j in tmpArrayEnemys)
{
// check if any of the blocks hit my ship!
if (tmpArrayEnemys[j].hitTestObject(player))
{
if (decreaseLivesAndCheckIfDead())
return; // stop the collision detection if i`m dead!!

tmpArrayEnemys[j].deleteEnemy();
}

for(var i in tmpArrayBullets)
{
// check if any of the bullets on the screen hits any enemies on the screen
//if (tmpArrayBullets[i].hitTestObject(tmpArrayEnemys[j]))
if(PixelPerfectCollisionDetection.isColliding(tmpArrayBullets[i],tmpArrayEnemys[j],this,true)==true)
{
if (tmpArrayEnemys[j].hitEnemy(tmpArrayBullets[i]))
{ //count only if we actually hits the block
myHitsNo++;
myScoreTxt.text = "Score: " + myHitsNo;

if (myHitsNo % 7 == 0)
{ // increase the speed every 7th hit
enemySpeed = enemySpeed + 1;
if (enemyLimit > 30)
{
enemyLimit = enemyLimit - 10;
}
}
}

tmpArrayBullets[i].deleteBullet();
}
}
}
}

public function addEnemy(event:Event):void // How enemies are added and randomized
{
if(enemyTime < enemyLimit)
{
enemyTime ++;
}
else
{
var newEnemy;
// randomize which enemy that should spawn
var number = Math.ceil(Math.random()*4);
if (number == 1)
{
newEnemy = new enemyEarth();
}
else if (number == 2)
{
newEnemy = new enemyFire();
}
else if (number == 3)
{
newEnemy = new enemyWater();
}
else if (number == 4)
{
newEnemy = new enemyIce();
}
newEnemy.x = -1 * newEnemy.width;

// randomize the spawn point for the enemy
var spawnPoint = Math.ceil(Math.random()*4);
if (spawnPoint == 1)
{
newEnemy.y = spawnPoint1;
}
else if (spawnPoint == 2)
{
newEnemy.y = spawnPoint2;
}
else if (spawnPoint == 3)
{
newEnemy.y = spawnPoint3;
}
else if (spawnPoint == 4)
{
newEnemy.y = spawnPoint4;
}

enemys.push(newEnemy);

addChild(newEnemy);
enemyTime = 0;

}
}
}
}