diff --git a/script.js b/script.js
index aebb512..8146bdc 100644
--- a/script.js
+++ b/script.js
@@ -18,7 +18,8 @@ var pressed = {
 var cfg = {
   fps: 60,
   width: 640,
-  height: 480
+  height: 480,
+  isGameOver: false
 };
 
 var $container = $('#container');
@@ -41,6 +42,7 @@ function Player (x, y) {
   this.health = 3;
   this.width = 50;
   this.height = 50;
+  this.timeSinceLastShot = 0;
   this.element = $('<div class="player">').appendTo($container);
 }
 
@@ -95,8 +97,11 @@ function setup () {
 function update () {
 
   // Spawn bullet
-  if (pressed.up) {
+  var currentTime = Date.now();
+  var bulletDelay = 100;
+  if (pressed.up && currentTime - player.timeSinceLastShot > bulletDelay) {
     bullets.push(new Bullet(player.position.x, player.position.y + player.height));
+    player.timeSinceLastShot = currentTime;
   }
 
   // Left-right movement
@@ -123,14 +128,31 @@ function update () {
 
   // TODO: Collision detection & health adjustment
 
-
+  for (var i = 0; i < bullets.length; i++){
+    var bullet = bullets[i];
+    for (var j = 0; j < enemies.length; j++){
+      var enemy = enemies[j];
+      if (isColliding(bullet, enemy)){
+        enemy.health--;
+        bullet.health--;
+        break;
+      }
+   
+    }
+  }
+  
+  for (var i = 0; i < enemies.length; i++){
+    var enemy = enemies[i];
+    if (isColliding(enemy, player)){
+      player.health--;
+    }
+  }
   // Player bounds checking
   if (player.position.x < 0) {
     player.position.x = 0;
   } else if (player.position.x > cfg.width) {
     player.position.x = cfg.width;
-  }
-
+  }1
   // Bullet bounds/health checking
   for (var i = bullets.length - 1; i >= 0; i--) {
     var bullet = bullets[i];
@@ -151,10 +173,36 @@ function update () {
   }
 
   // TODO: Lose condition (i.e. if player is dead)
+  if (!cfg.isGameOver && player.health <= 0){
+    player.element.remove();
+    cfg.isGameOver = true;
+    alert('You Lose');
+  }
 
   // TODO: Win condition (i.e. if all enemies are dead)
+  if (!cfg.isGameOver && enemies.length === 0){
+    cfg.isGameOver = true;
+    alert('You Win');
+  }
+}
+function isColliding (e1, e2){
+  var e1left = e1.position.x - e1.width/2;
+  var e1right = e1.position.x + e1.width/2;
+  var e1top = e1.position.y + e1.height/2;
+  var e1bottom = e1.position.y - e1.height/2;
+  
+  var e2left = e2.position.x - e2.width/2;
+  var e2right = e2.position.x + e2.width/2;
+  var e2top = e2.position.y + e2.height/2;
+  var e2bottom = e2.position.y - e2.height/2;
+  
+  return !(
+    e1bottom > e2top ||
+    e1top < e2bottom ||
+    e1left > e2right ||
+    e1right  < e2left
+    );
 }
-
 // Enemy attack movement
 function runEnemyAI (enemies) {
   var attackingEnemy;