<!-- question 4 -->
			var fish;
            var imageSchedule;

            function startAnimation(){
				var fishImage = document.getElementById("fish");
				fishImage.src = "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png";
				imageSchedule = setInterval(showimage,  1000);
            }

            function showimage(){

				var fishImage = document.getElementById("fish");

				if (fishImage.src == "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png") {
					fishImage.src = "https://www.uow.edu.au/~dong/w3/assignment/a5/sad_fish.png";

				}

                else if (fishImage.src == "https://www.uow.edu.au/~dong/w3/assignment/a5/sad_fish.png") {
                         fishImage.src = "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png";
                }

            }

            function stopAnimation(){
				clearInterval(imageSchedule);

            }

			<!-- question 5 -->
			var image;
            var imageSchedule;
            var image2 = 0;
            var userScore = 0 ;

            function startGame(){
                var image2 = document.getElementById("image1");
                image2.src = "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png";
                imageSchedule = setInterval(showFish,  1000);
            }



            function showFish(){

				var image2 = document.getElementById("image1");

                if (image2.src == "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png") {
                    image2.src = "https://www.uow.edu.au/~dong/w3/assignment/a5/sad_fish.png";

                }

					else if (image2.src == "https://www.uow.edu.au/~dong/w3/assignment/a5/sad_fish.png") {
                        image2.src = "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png";
                    }

            }

			function stopGame(){
                clearInterval(imageSchedule);

            }

            function score(){
				var image = document.getElementById("image1");

				if (image.src == "https://www.uow.edu.au/~dong/w3/assignment/a5/happy_fish.png") {
					userScore += 5;
				}
					else if (image.src == "https://www.uow.edu.au/~dong/w3/assignment/a5/sad_fish.png"){
						userScore -= 5;
					}

                var span = document.getElementById("image_1");
                span.innerHTML = userScore;

                if (userScore == 10){
					span.innerHTML = userScore + " you win" ;

				}
					else if (userScore == - 10){
						span.innerHTML = userScore + " you lose" ;

					}

            }

  <button onclick="startAnimation()" > Start Animation </button>

            <button onclick="stopAnimation()" > Stop Animation </button>

            <br>
            <br>

            <img id="fish">

		<hr>

			<button onClick="startGame()"> Start Animation </button>

            <button onClick="stopGame()"> Stop Animation </button>

			<br>
            <br>
            <br>

            <img id="image1" onclick="score()">

            <br>

            Your score: <span id="image_1" ></span>