{{ block title }}
    Welcome & Instructions
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{{ block content }}
<div class="card bg-light m-3">
    <div class="card-body">
        <h4 class="card-title text-primary">Welcome</h4>
        <p>This is a study about classifying images.</p>
        <p>The whole session will last for <strong>30 to 35 minutes</strong>. The participation payment you will receive for completing the session is <strong>$5</strong>, and there is one possible additional bonus payments of <strong>$2.50</strong>. Your performance during the session will determine the likelihood you receive the bonus payments.</p>
        <p>You will see some instructions over the next few pages, please read them carefully.</p>
        
        <hr>

        <h4 class="card-title text-primary">Instructions</h4>
        <p>In this session, you will be shown <strong>images</strong> of people one at a time.</p>
        <p>For each image, you will be asked the <strong>probability</strong> (from 0% to 100%) that you think the person was over 21 years old when the image was taken. For example, if you were presented with the following image, you would be asked the probability you think the person was over 21 years old.</p>
        <p>After seeing 160 images, you will be asked to complete a very brief survey to ensure data collection and an additional task to determine your bonus payment.</p>

        <hr>

        <h5 class="text-secondary">Payment</h5>
        <p>The <strong>participation payment</strong> is $5, which you will get if you <strong>finish</strong> the session.</p>
        <p>The <strong> possible bonus payment</strong> is an <strong>additional $2.50</strong>. At the end of the session, one of the images will be selected at random to determine your bonus payment. The payment rule for the randomly selected image is designed so that you maximize your overall likelihood of getting the bonus payment when you <strong>truthfully report your belief that the person in the image was over 21</strong>.</p>
        <hr>

        <h5 class="text-secondary">Helpful tips</h5>
        <ol>
            <li>All images were taken between 2010 and 2014.</li>
            <li>Half (50%) of the 160 images are of people who were under 21 years old (that is, 20 years and younger) and the other half are people who were over 21 years old (that is, 22 years and older). None of the images are of people 21 years old.</li>
            <li>For each image, you will have <strong>60 seconds</strong> to enter the probability you think the person in the image was over 21 years old.</li>
            <li>If you <strong>do not submit</strong> your answer within the time limit, you will have a 0% chance of winning the bonus payment if the image is randomly selected for payment.</li>
            <li>You will not be able to go back to previously seen images.</li>
        </ol>
        <p>Before beginning, you have <strong>1 practice image</strong>, which will not impact your payment.</p>
        
        <p class="text-muted mt-4"><em>To make sure you have read the instructions, the next button will be activated after 10 seconds.</em></p>
    </div>
</div>

<div class="alert alert-info mt-4">
    <label for="manual_pid" class="form-label"><strong>Prolific ID:</strong></label>
    <input type="text" id="manual_pid" class="form-control" placeholder="e.g. 5f9a3b..." required>
    <small class="form-text text-muted" id="pid-help-text">
        For privacy and IRB compliance, this ID is strictly kept in your browser for payment routing and will NOT be stored in our experimental database.
    </small>
</div>

<div class="text-center mt-4" id="next-btn-container" style="display: none;">
    <button class="btn btn-primary btn-lg" id="submit-btn">Next</button>
</div>

<script>
    const pidInput = document.getElementById('manual_pid');
    const helpText = document.getElementById('pid-help-text');

    // 【新增逻辑】：直接从第一页（Consent）存好的保险箱里拿 PID
    const savedPid = sessionStorage.getItem('my_prolific_id');

    if (savedPid) {
        pidInput.value = savedPid;
        helpText.innerHTML = "<em>✅ We have automatically detected your Prolific ID. Please verify it and click Next.</em> (This ID is strictly kept in your browser for payment routing.)";
    }

    // 10秒后显示 Next 按钮
    setTimeout(function() {
        document.getElementById('next-btn-container').style.display = 'block';
    }, 10000);

    // 点击 Next 时，以防受试者手动改了，再更新一次保险箱
    document.getElementById('submit-btn').addEventListener('click', function(e) {
        const finalPid = pidInput.value.trim();
        
        if (finalPid === "") {
            e.preventDefault(); 
            alert("Please enter your Prolific ID before continuing.");
        } else {
            sessionStorage.setItem('my_prolific_id', finalPid);
        }
    });
</script>
{{ endblock }}