How can I modify my CSS and HTML to support mobile view

Question

My teacher demand to modify my CSS and HTML to support mobile view if it is necessary. I have to follow as below:

If the page is viewed on mobile:

o The viewport should be set to zoom-level 100%, and the width should be the device-width

• If the device screen size is less than 700px wide:

o The width of the page content should be 95% instead of 700px

• If the device screen size is less than 500px wide:

o The yellow circles in the page header should not appear( it is the "MERN" displayed in the right top corner)

I don't know how to code it. Thank you so much

body {
    font-family: "Proxima Nova", Arial, Helvetica, sans-serif;
    font-size: 18px;
    color: #222222;
    display: flex;
    justify-content: space-around;
    align-items: center;
    flex-direction: column;
}

header {
    border-bottom: 1px solid #ccc;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-direction: row;
    width: 700px;
    height: 80px;
}

#coursename {
    font-family: Helvetica, sans-serif;
    font-size: 32px;
    font-weight: bold;
    color: #ee3322;
}

header span {
    display: flex;
    justify-content: space-around;
    align-items: center;
    flex-direction: row;
}

#MRN {
    height: 50px;
    display: flex;
    justify-content: space-around;
    flex-direction: row;
    align-items: center;
}

#MRN span {
    background-color: #ffee00;
    border-radius: 100%;
    height: 50px;
    width: 50px;
    margin: 3px;
    text-align: center;
    transform: rotate(-30deg);
    font-weight: bold;
}

#MRN div {
    background-color: #ffee00;
    border-radius: 100%;
    width: 50px;
    height: 50px;
    text-align: center;
    transform: rotate(-30deg);
    padding: 10px;
}

article {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}

#quiz-name {
    background-image: url(../starter_pack/images/background.jpg);
    background-repeat: no-repeat;
    background-size: cover;
    background-position: middle;
    width: 700px;
    height: 425px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

h1 {
    background-color: rgba(255, 255, 255, 0.9);
    font-family: Pangolin, "Trebuchet MS", cursive;
    font-size: 60px;
    color: black;
    padding: 10px;
    max-width: 75%;
    text-align: center;
    display: flex;
    justify-content: center;
    align-items: center;
}

#author {
    font-size: 14px;
    text-align: center;
    margin-top: 18px;
}

#introduction {
    width: 700px;
}

#introduction h2,
#introduction p {
    margin: 18px 0 18px 0;
}

#startquiz,
#tryagain {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border: 1px solid #f1f1f1;
    background-color: #f1f1f1;
    padding: 18px;
}

button {
    border: none;
    color: white;
    background-color: #2196f3;
    padding: 18px;
}

button:hover {
    background-color: #0d8bf2;
}

#attempt-quiz,
#review-quiz {
    width: 700px;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    flex-direction: column;
}

#attempt-quiz p,
#review-quiz p {
    margin: 30px 0 30px 0;
}

form {
    cursor: pointer;
    width: 700px;
    margin: 30px 0 30px 0;
}

.option,
.review-answer {
    border-top: 1px solid white;
    border-bottom: 1px solid white;
    display: flex;
    justify-content: flex-start;
    align-items: center;
    flex-direction: row;
    width: auto;
    padding: 15px;
    background-color: #f1f1f1;
    position: relative;
}

.option:hover {
    background-color: #ddd;
}

label {
    margin-left: 15px;
}

.correct {
    position: absolute;
    right: 0;
    margin: 10px;
    background-color: rgba(0, 0, 0, 0.2);
    padding: 3px;
    color: white;
}

.incorrect {
    position: absolute;
    right: 0;
    margin: 10px;
    background-color: rgba(0, 0, 0, 0.2);
    padding: 3px;
    color: white;
}

#submit {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    margin-top: 18px;
    border: 1px solid #f1f1f1;
    background-color: #f1f1f1;
    padding: 18px;
}

#submit button {
    border: none;
    color: white;
    background-color: #4caf50;
    padding: 18px;
}

#submit button:hover {
    background-color: #46a049;
}

.hidden {
    display: none;
}

#tryagain {
    background-color: #f1f1f1;
    border: 1px solid #dcdcdc;
}

#tryagain h3 {
    font-size: 24px;
    font-weight: lighter;
}

.option {
    position: relative;
    padding: 0;
}

.option input[type="radio"] {
    position: absolute;
    left: 10px;
    top: 15px;
}

.option label {
    flex-grow: 1;
    padding: 15px 40px;
    margin: 0;
}

.option input[type="radio"]:checked+label {
    background: #ddd;
}

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>HTML Quiz</title>
    <link rel="icon" type="image/png" href="images/favicon-32x32.png" sizes="32x32" />
    <link rel="icon" type="image/png" href="images/favicon-16x16.png" sizes="16x16" />
    <link href="https://fonts.googleapis.com/css?family=Pangolin:400,700|Proxima+Nova" rel="stylesheet" type="text/css">
    <link rel="stylesheet" href="style.css" />
    <script src="script.js" defer="true"></script>
</head>

<body>

    <header>

        <p id="coursename"><strong> WPR </strong> </p>
        <div id="MRN">

            <span>M</span>
            <span>E</span>
            <span>R</span>
            <span>N</span>
        </div>
    </header>


    <article>
        <section id="quiz-name">
            <h1 id="hello">HTML Quiz</h1> <br>
        </section>

        <p id="author"> By Minh Duc Nguyen </p>

        <section id="introduction">
            <h2> The Test </h2>


            <p>The test contains 10 questions and there is no time limit.</p>

            <p>The test is not official, it's just a nice way to see how much you know, or don't know, about HTML.</p>

            <h2>Count Your Score</h2>
            <p>
                You will get 1 point for each correct answer. At the end of the Quiz, your total score will be displayed. Maximum score is 10 points.
            </p>
            <div id="startquiz">
                <h2>Start the quiz</h2>
                <p> Good luck!</p>
                <button name="button" type="button">Start the HTML quiz ❯ </button>
            </div>
        </section>

        <section id="attempt-quiz">
            <div id="quiz">
                <p><strong> Question 1 of 10</strong></p>
                <p>Question 1</p>
                <form name="ques01" id='ques01'>
                    <div class="option">
                        <input type="radio" name="question1" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question1" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question1" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question1" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 2 of 10</strong></p>
                <p>Question 2</p>
                <form name="ques02" id='ques02'>
                    <div class="option">
                        <input type="radio" name="question2" value="option 1">
                        <label><div >option 1 </div></label><br>
                    </div>
                    <div class="option">
                        <input type="radio" name="question2" value="option 2">
                        <label>option 2</label><br>
                    </div>
                    <div class="option">
                        <input type="radio" name="question2" value="option 3">
                        <label>option 3</label><br>
                    </div>
                    <div class="option">
                        <input type="radio" name="question2" value="option 4">
                        <label>option 4</label><br>
                    </div>
                </form>

                <p><strong> Question 3 of 10</strong></p>
                <p>Question 3</p>
                <form name="ques03" id='ques03'>
                    <div class="option">
                        <input type="radio" name="question3" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question3" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question3" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question3" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 4 of 10</strong></p>
                <p>Question 4</p>
                <form name="ques04" id='ques04'>
                    <div class="option">
                        <input type="radio" name="question4" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question4" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question4" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question4" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 5 of 10</strong></p>
                <p>Question 5</p>
                <form name="ques05" id='ques05'>
                    <div class="option">
                        <input type="radio" name="question5" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question5" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question5" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question5" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 6 of 10</strong></p>
                <p>Question 6</p>
                <form name="ques06" id='ques06'>
                    <div class="option">
                        <input type="radio" name="question6" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question6" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question6" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question6" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 7 of 10</strong></p>
                <p>Question 7

                </p>
                <form name="ques07" id='ques07'>
                    <div class="option">
                        <input type="radio" name="question7" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question7" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question7" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question7" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 8 of 10</strong></p>
                <p>Question 8</p>
                <form name="ques08" id='ques08'>
                    <div class="option">
                        <input type="radio" name="question8" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question8" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question8" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question8" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 9 of 10</strong></p>
                <p>Question 9</p>
                <form name="ques09" id='ques09'>
                    <div class="option">
                        <input type="radio" name="question9" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question9" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question9" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question9" value="option 4">
                        <label>option 4</label><br>

                    </div>
                </form>

                <p><strong> Question 10 of 10</strong></p>
                <p>Question 10</p>
                <form name="ques10" id='ques10'>
                    <div class="option">
                        <input type="radio" name="question10" value="option 1">
                        <label><div >option 1 </div></label><br>


                    </div>
                    <div class="option">
                        <input type="radio" name="question10" value="option 2">
                        <label>option 2</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question10" value="option 3">
                        <label>option 3</label><br>

                    </div>
                    <div class="option">
                        <input type="radio" name="question10" value="option 4">
                        <label>option 4</label><br>
                    </div>
                </form>
                <div id="submit">
                    <button type="submit" value="submit" onclick="totalscore()">Submit your answer</button>
                </div>
                </form>
            </div>
        </section>
   
    </article>
</body>


</html>

Answer 1

You should use CSS media queries. These is the updated CSS file.

body {
    font-family: "Proxima Nova", Arial, Helvetica, sans-serif;
    font-size: 18px;
    color: #222222;
    display: flex;
    justify-content: space-around;
    align-items: center;
    flex-direction: column;
    width:100%
}

header {
    border-bottom: 1px solid #ccc;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-direction: row;
    width: 700px;
    height: 80px;
}

#coursename {
    font-family: Helvetica, sans-serif;
    font-size: 32px;
    font-weight: bold;
    color: #ee3322;
}

header span {
    display: flex;
    justify-content: space-around;
    align-items: center;
    flex-direction: row;
}

#MRN {
    height: 50px;
    display: flex;
    justify-content: space-around;
    flex-direction: row;
    align-items: center;
}

#MRN span {
    background-color: #ffee00;
    border-radius: 100%;
    height: 50px;
    width: 50px;
    margin: 3px;
    text-align: center;
    transform: rotate(-30deg);
    font-weight: bold;
}

@media all and (max-width :500px){
  #MRN span{
    display:none;
  }
}

#MRN div {
    background-color: #ffee00;
    border-radius: 100%;
    width: 50px;
    height: 50px;
    text-align: center;
    transform: rotate(-30deg);
    padding: 10px;
}

article {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
}

#quiz-name {
    background-image: url(../starter_pack/images/background.jpg);
    background-repeat: no-repeat;
    background-size: cover;
    background-position: middle;
    width: 700px;
    height: 425px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

h1 {
    background-color: rgba(255, 255, 255, 0.9);
    font-family: Pangolin, "Trebuchet MS", cursive;
    font-size: 60px;
    color: black;
    padding: 10px;
    max-width: 75%;
    text-align: center;
    display: flex;
    justify-content: center;
    align-items: center;
}

#author {
    font-size: 14px;
    text-align: center;
    margin-top: 18px;
}

#introduction {
    width: 700px;
}

#introduction h2,
#introduction p {
    margin: 18px 0 18px 0;
}

#startquiz,
#tryagain {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    border: 1px solid #f1f1f1;
    background-color: #f1f1f1;
    padding: 18px;
}

button {
    border: none;
    color: white;
    background-color: #2196f3;
    padding: 18px;
}

button:hover {
    background-color: #0d8bf2;
}

#attempt-quiz,
#review-quiz {
    width: 700px;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    flex-direction: column;
}

#attempt-quiz p,
#review-quiz p {
    margin: 30px 0 30px 0;
}

form {
    cursor: pointer;
    width: 700px;
    margin: 30px 0 30px 0;
}

.option,
.review-answer {
    border-top: 1px solid white;
    border-bottom: 1px solid white;
    display: flex;
    justify-content: flex-start;
    align-items: center;
    flex-direction: row;
    width: auto;
    padding: 15px;
    background-color: #f1f1f1;
    position: relative;
}

.option:hover {
    background-color: #ddd;
}

label {
    margin-left: 15px;
}

.correct {
    position: absolute;
    right: 0;
    margin: 10px;
    background-color: rgba(0, 0, 0, 0.2);
    padding: 3px;
    color: white;
}

.incorrect {
    position: absolute;
    right: 0;
    margin: 10px;
    background-color: rgba(0, 0, 0, 0.2);
    padding: 3px;
    color: white;
}

#submit {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    margin-top: 18px;
    border: 1px solid #f1f1f1;
    background-color: #f1f1f1;
    padding: 18px;
}

#submit button {
    border: none;
    color: white;
    background-color: #4caf50;
    padding: 18px;
}

#submit button:hover {
    background-color: #46a049;
}

.hidden {
    display: none;
}

#tryagain {
    background-color: #f1f1f1;
    border: 1px solid #dcdcdc;
}

#tryagain h3 {
    font-size: 24px;
    font-weight: lighter;
}

.option {
    position: relative;
    padding: 0;
}

.option input[type="radio"] {
    position: absolute;
    left: 10px;
    top: 15px;
}

.option label {
    flex-grow: 1;
    padding: 15px 40px;
    margin: 0;
}

.option input[type="radio"]:checked+label {
    background: #ddd;
}

@media all and (max-width:700px){
  header, form, #attempt-quiz, #review-quiz, #url, #introduction, header{
    width:95% !important;
    font-size:1rem;
  }
}