Instruction Step 1: Create a snippet and name it sticky-atc-custom and the paste the code given below:

{% comment %}
  Renders sticky product add to cart button.
  Accepts:
  - product: {Object} product object.
  - block: {Object} passing the block information.
  - product_form_id: {String} product form id.
  - section_id: {String} id of section to which this snippet belongs.

  Usage:
  {% render 'sticky-atc-custom', block: block, product: product, product_form_id: product_form_id, section_id: section.id %}
{% endcomment %}

{% assign has_variants = true %}
{% if product.options.size == 1 and product.options.first == 'Title' %}
  {% assign has_variants = false %}
{% endif %}
    
<product-form
  class="product-form sticky-atc"
  data-hide-errors="{{ gift_card_recipient_feature_active }}"
  data-section-id="{{ section.id }}"
>

      <div class="product-form__error-message-wrapper" role="alert" hidden>
        <svg
          aria-hidden="true"
          focusable="false"
          class="icon icon-error"
          viewBox="0 0 13 13"
        >
            <circle cx="6.5" cy="6.50049" r="5.5" stroke="white" stroke-width="2"/>
            <circle cx="6.5" cy="6.5" r="5.5" fill="#EB001B" stroke="#EB001B" stroke-width="0.7"/>
              <path d="M5.87413 3.52832L5.97439 7.57216H7.02713L7.12739 3.52832H5.87413ZM6.50076 9.66091C6.88091 9.66091  7.18169 9.37267 7.18169 9.00504C7.18169 8.63742 6.88091 8.34917 6.50076 8.34917C6.12061 8.34917 5.81982 8.63742 5.81982 9.00504C5.81982 9.37267 6.12061 9.66091 6.50076 9.66091Z" fill="white"/>
              <path d="M5.87413 3.17832H5.51535L5.52424 3.537L5.6245 7.58083L5.63296 7.92216H5.97439H7.02713H7.36856L7.37702 7.58083L7.47728 3.537L7.48617 3.17832H7.12739H5.87413ZM6.50076 10.0109C7.06121 10.0109 7.5317 9.57872 7.5317 9.00504C7.5317 8.43137 7.06121 7.99918 6.50076 7.99918C5.94031 7.99918 5.46982 8.43137 5.46982 9.00504C5.46982 9.57872 5.94031 10.0109 6.50076 10.0109Z" fill="white" stroke="#EB001B" stroke-width="0.7">
        </svg>
        <span class="product-form__error-message"></span>
      </div>

      <div class="content-container">
          <div class="selected-variant-title mobile-title">{{ product.title }}</div>  
          <div class="product-details-container">
              <div class="selected-variant-header-container">
                  <div class="selected-variant-image-container">
                    {% if product.selected_or_first_available_variant.image %}
                      <img src="{{ product.selected_or_first_available_variant.image.src | img_url}}" alt="Selected Variant Image" id="selectedVariantImage">
										{% elsif has_variants == false and product.images.size > 0 %}
                      <img src="{{ product.images.first.src | img_url }}" alt="Product Image" id="selectedVariantImage">
                    {% endif %}
                  </div>
                  <div class="selected-variant-title desktop-title">{{ product.title }}</div> 
              </div>
              <div class="product-info-container">              
                  <div class="selected-variant-details">
                      <!-- Dynamically show selected variant details here -->
                      <div class="options-container {% if has_variants == false %}hide-variant-options{% endif %}">
                          {% for option in product.options %}
                              <div class="selected-variant-option" data-option-name="{{ option }}">
                                  {{ option }}: {{ product.selected_or_first_available_variant.options[forloop.index0] }}
                              </div>
                          {% endfor %}
                      </div>
                      <div class="price-container">
                          <span class="compared-price" style="{% unless product.selected_or_first_available_variant.compare_at_price > product.selected_or_first_available_variant.price %}display:none;{% endunless %}">{{ product.selected_or_first_available_variant.compare_at_price | money }}</span>
                          <span class="selection-price">{{ product.selected_or_first_available_variant.price | money }}</span>
                          {%- assign difference = product.selected_or_first_available_variant.compare_at_price | minus: product.selected_or_first_available_variant.price -%}
                          {%- assign float_difference = difference | times: 1.0 -%}
                          {%- assign discount_fraction = float_difference | divided_by: product.selected_or_first_available_variant.compare_at_price -%}
                          {%- assign discount_percentage = discount_fraction | times: 100 | round -%}
                          &nbsp;
                          <span class="selection-price discount-percentage" style="{% unless product.selected_or_first_available_variant.compare_at_price > product.selected_or_first_available_variant.price %}display:none;{% endunless %}">(Save {{ discount_percentage }}%)</span>
                      </div>
                  </div>
            
            
                  <div class="atc-button-container">      
                      {%- form 'product',
                        product,
                        id: product_form_id,
                        class: 'form',
                        novalidate: 'novalidate',
                        data-type: 'add-to-cart-form'
                      -%}
                        <input
                          type="hidden"
                          name="id"
                          value="{{ product.selected_or_first_available_variant.id }}"
                          disabled
                          class="product-variant-id"
                        >
                
                        {%- if gift_card_recipient_feature_active -%}
                          {%- render 'gift-card-recipient-form', product: product, form: form, section: section -%}
                        {%- endif -%}
                
                        <div class="product-form__buttons sticky-product-form__buttons">
                          {%- liquid
                            assign check_against_inventory = true
                            if product.selected_or_first_available_variant.inventory_management != 'shopify' or product.selected_or_first_available_variant.inventory_policy == 'continue'
                              assign check_against_inventory = false
                            endif
                            if product.selected_or_first_available_variant.quantity_rule.min > product.selected_or_first_available_variant.inventory_quantity and check_against_inventory
                              assign quantity_rule_soldout = true
                            endif
                          -%}
                          <button
                            id="StickyProductSubmitButton-{{ section_id }}"
                            type="submit"
                            name="add"
                            class="product-form__submit button button--full-width button--primary sticky-atc-button"
                            {% if product.selected_or_first_available_variant.available == false or quantity_rule_soldout %}
                              disabled
                            {% endif %}
                          >
                            <span>
                              {%- if product.selected_or_first_available_variant.available == false or quantity_rule_soldout -%}
                                {{ 'products.product.sold_out' | t }}
                              {%- else -%}
                                {{ 'products.product.add_to_cart' | t }}
                              {%- endif -%}
                            </span>
														{%- render 'loading-spinner' -%}
                          </button>
                        </div>
                      {%- endform -%}
                  </div>
              </div>

          </div>
      </div>
</product-form>


            
<script>

    document.addEventListener("DOMContentLoaded", function() {
        var atcElement = document.querySelector(".sticky-atc");
        var targetElement = document.querySelector('[id^="ProductSubmitButton-"]');
    
        function getAbsoluteTop(element) {
            var top = 0;
            while (element) {
                top += element.offsetTop || 0;
                element = element.offsetParent;
            }
            return top;
        }
    
        window.addEventListener("scroll", function() {
            var targetTopPosition = getAbsoluteTop(targetElement);
            var targetBottomPosition = targetTopPosition + targetElement.clientHeight;
    
            // console.log("Current Scroll Position:", window.scrollY);
            // console.log("Target Element Bottom Position:", targetBottomPosition);
    
            var isTargetElementOutOfView = targetTopPosition < window.scrollY; // Using top position because of sticky menubar
            //var isTargetElementOutOfView = targetBottomPosition < window.scrollY; //Element is completely out of window
    
            // console.log("Is Target Element Out of View:", isTargetElementOutOfView);
    
            if (isTargetElementOutOfView) {
                atcElement.classList.add('show'); // This will make it slide up
            } else {
                atcElement.classList.remove('show'); // This will make it slide down
            }
        });
    
        // Reference to the variant input in the sticky ATC form
        var stickyAtcVariantInput = document.querySelector('.sticky-atc .product-variant-id');
    
    
        // Function to handle variant change and update the sticky ATC form
        function updateStickyATCOption(optionName, optionValue) {
            // Extract option name if it's in the format options[OptionName]
            var matches = optionName.match(/options\[(.+)\]/);
            if (matches && matches[1]) {
                optionName = matches[1];
            }
            // console.log("Updating option:", optionName, "with value:", optionValue);  // Debug statement
          
            var optionDisplay = document.querySelector('.selected-variant-option[data-option-name="' + optionName + '"]');
            if (optionDisplay) {
                optionDisplay.textContent = optionName + ': ' + optionValue;
            }
          
    
          
        }
    
        function handleVariantChange(event) {
            var target = event.target;
            if (target.tagName === 'INPUT' || target.tagName === 'SELECT') {
                var optionName = target.name;
                var optionValue = target.tagName === 'INPUT' ? target.value : target.options[target.selectedIndex].textContent;
                updateStickyATCOption(optionName, optionValue);
            }
        }
    
        document.body.addEventListener('change', handleVariantChange);
    
        // The function to update the variant prices is found in the global.js renderProductInfo function
        // The function to update the variant image is found in the global.js updateMedia function
    });


</script>


            
<style>

	.options-container.hide-variant-options {
	    display: none;
	}

    .mobile-title {
        display: flex;
        font-size: 11px;
    }
    .desktop-title {
        display: none;
    }
      
    @media (min-width: 750px) {
        .mobile-title {
            display: none;
        }
        .desktop-title {
            display: flex;
            font-size: 15px;
        } 
    }
    
    
      
    .content-container {
        display: flex;
        flex-direction: column; /* To stack its children vertically */
        flex: 1; /* Allow it to take up the remaining space */
        align-items: stretch; /* Make children take full width */
    }
    
    
      
    .product-details-container {
        display: flex;
        justify-content: space-between;
        align-items: center;
        flex: 1; /* Allow it to take up the remaining space */
    }
    
    
    /* Use flexbox for the product form */
    .product-form.sticky-atc {
        display: flex;
        justify-content: space-between; /* Spread children horizontally */
        align-items: center; /* Center children vertically */
    }
    
    /* The product info and button container will take up the remaining space */
    .product-info-container {
        flex: 1; /* Take up all available space */
        display: flex;
        flex-direction: column;
        justify-content: center;
    }
    
    /* The image container will only take up as much space as it needs */
    .selected-variant-image-container {
        flex-shrink: 0; /* Prevent shrinking */
        height: 64px; Adjust as per your requirement
        overflow: hidden; 
        margin-left: 0px; /* Add some space between product info and image */
        margin-right: 10px; /* Space between image and right edge of screen */
        display: flex; /* Used to center the image both vertically and horizontally */
        align-items: center; /* Vertically center the image */
        justify-content: center; /* Horizontally center the image */
    }
      
    #selectedVariantImage {
        max-height: 100%; /* Ensures image doesn't exceed container height 
        width: auto;       Auto width to maintain aspect ratio */
    }
    
    #StickyProductSubmitButton-{{ section_id }} {
        margin-bottom: 0px;  
    }
      
    .sticky-atc {
        /* display: none; */
        position: fixed;
        bottom: -200px;
        left: 0;
        z-index: 2;
        width: 100%;
        align-items: center;    
        background-color: #fff; /* or any desired color */
        border: 1px solid #e0e0e0; /* optional */
        border-radius: 4px; /* optional */
        box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1); /* optional for a subtle shadow */
        padding: 10px 10px; /* Optional: for some spacing */
        transition: bottom 0.3s ease-out; /* This adds the smooth slide animation */
    }
    
    .sticky-atc.show {
        bottom: 0; /* This will make the sticky ATC box slide up */
    }
      
    .selected-variant-title {
        /* display: block; Makes it take the full width */
        padding: 0px 0; /* Adds some spacing above and below the title */
        font-weight: bold;
        font-size: 12px; 
        text-align: left; /* Centers the text */
    }
    
      
    .selected-variant-option {
        color: #666; /* optional for a subtle color */
        font-size: 12px;
    }
    
      
    .selected-variant-details {
        display: flex;
        flex-direction: column; /* Stack children vertically */
        justify-content: center; /* Center them vertically */
        align-items: center; 
    }
    
    
    
    .options-container {
        width: 100%;
        display: grid;
        grid-template-columns: 65% 35%;
        column-gap: 10px;
        align-items: flex-end;
    }
    
    
    
    .selected-variant-option {
        white-space: nowrap; /* Prevent text from wrapping within the element */
        overflow: hidden;
        text-overflow: ellipsis;
        max-width: 100%; /* Ensures that the option doesn't overflow its container */
        flex-shrink: 0; /* Prevent the option from shrinking */
        flex-grow: 0; /* Prevent the option from growing */
        align-items: center;
    }
    
      
    .price-container {
        display: flex;
        justify-content: flex-start; /* Adjust horizontally */
        align-items: center;
        width: 100%; /* Take up full width */
        /* margin-top: 10px;  Add some top margin for spacing */
    }
    
    .selection-price {
        font-size: 12px; /* Adjust font size as needed */
        font-weight: bold;
        color: #d53600; /* Adjust color as needed */
    }
      
    .compared-price {
        font-size: 10px; /* Adjust font size as needed */
        text-decoration: line-through;
        color: #888; /* A lighter color to indicate it's the old price */
        margin-right: 10px; /* Space between actual price and compared price */
    }
    
    .atc-button-container {
        align-items: center !important;
    }
    
    
    /* This media query targets devices with a width of 750px and above (desktops) */   
      
    @media (min-width: 750px) {
    
        .sticky-atc {
            bottom: auto; /* Reset the bottom property for desktop */
            top: -200px; /* Start off-screen */
            transition: bottom 0.3s ease-out; /* Transition for desktop */
            padding-top: 5px;
            padding-bottom: 5px;
        }
        
        .sticky-atc.show {
            top: auto; /* Reset the bottom property for desktop */
            bottom: 0px; /* Or the height of your sticky menubar if you have one */
        }
    
        .product-details-container {
            gap: 20px; 
        }
        .selected-variant-header-container {
            display: flex;
            flex: 0 0 40%;
            align-items: center;
            flex: 1; /* Allow it to take up the remaining space */
        }
    
     
        .selected-variant-image-container {
            height: 50px;  Adjust as per your requirement */
        }
          
        .product-info-container {
            flex: 0 0 60%;
            flex-direction: row; /* On desktop, layout children horizontally */
        }
        .selected-variant-details {
            flex-direction: row;
            flex: 0 0 70%;  /* 70% of the parent's width */
            justify-content: space-between;
            padding: 0px 10px;
        }
    
        .selected-variant-option {
            justify-content: center; 
        }
          
        .options-container {
            flex: 0 0 50%;  /* 55% of the parent's width */
        }
        
        .price-container {
            flex: 0 0 50%;  /* 45% of the parent's width */
            justify-content: right;
        }
      
        .atc-button-container {
            flex: 0 0 30%;  /* 30% of the parent's width */
            max-width: 40rem;
        }
      
    }
    
    @media (min-width: 990px) {
    
        .sticky-atc.show {
           bottom: 0px; /* Or the height of your sticky menubar if you have one */
        }
    }
      
  
</style>






Instruction Step 2: Now go to global.js and search updatemedia then enter the code given below (follow the video carefully)

// Update the ATC box image
    const atcBoxImage = document.querySelector('#selectedVariantImage');
    if (newMediaModal && newMediaModal.src && atcBoxImage) {
        atcBoxImage.src = newMediaModal.src;
    }
    
Instruction Step 3: In global.js search renderproductinfo and paste the code given below (follow the video carefully)

//Update Sticky ATC Product Info
const regularPriceElement = source.querySelector('.price__sale s.price-item--regular') || source.querySelector('.price__regular .price-item--regular');
const salePriceElement = source.querySelector('.price__sale .price-item--sale');

const stickyAtcRegularPrice = document.querySelector('.sticky-atc .compared-price');
const stickyAtcSalePrice = document.querySelector('.sticky-atc .selection-price');
const stickyAtcDiscount = document.querySelector('.sticky-atc .discount-percentage');

if (regularPriceElement && stickyAtcRegularPrice) {
    stickyAtcRegularPrice.textContent = regularPriceElement.textContent;
}

if (salePriceElement && stickyAtcSalePrice) {
    stickyAtcSalePrice.textContent = salePriceElement.textContent;
}

if (regularPriceElement && salePriceElement) {
    // Extract numerical values
    let compareAtPrice = parseFloat(regularPriceElement.textContent.replace('$', ''));
    let price = parseFloat(salePriceElement.textContent.replace('$', ''));

    // Calculate discount percentage
    let difference = compareAtPrice - price;
    let discountFraction = difference / compareAtPrice;
    let discountPercentage = Math.round(discountFraction * 100);

    // Update the sticky ATC box with the discount percentage
    if (stickyAtcDiscount) {
        stickyAtcDiscount.textContent = `(Save ${discountPercentage}%)`;
    }

    if (compareAtPrice > price) {
        // Show compared price and discount percentage
        if(stickyAtcRegularPrice) stickyAtcRegularPrice.style.display = 'inline';
        if(stickyAtcDiscount) stickyAtcDiscount.style.display = 'inline';
    } else {
        // Hide compared price and discount percentage
        if(stickyAtcRegularPrice) stickyAtcRegularPrice.style.display = 'none';
        if(stickyAtcDiscount) stickyAtcDiscount.style.display = 'none';
    }
}

const stickyAddButtonUpdated = html.getElementById(`StickyProductSubmitButton-${sectionId}`);
this.toggleStickyAddButton(
    stickyAddButtonUpdated ? stickyAddButtonUpdated.hasAttribute('disabled') : true,
    window.variantStrings.soldOut
);


Instruction Step 4: In global.js search toggleAddButton and paste the code given below as shown in the video

toggleStickyAddButton(disable = true, text, modifyClass = true) {
    const stickyProductForm = document.querySelector('.sticky-atc');
    
    if (!stickyProductForm) return;
  
    const stickyAddButton = stickyProductForm.querySelector('[name="add"]');
    const stickyAddButtonText = stickyAddButton.querySelector('[name="add"] > span');
  
    if (!stickyAddButton) return;
  
    if (disable) {
      stickyAddButton.setAttribute('disabled', 'disabled');
      if (text) stickyAddButtonText.textContent = text;
    } else {
      stickyAddButton.removeAttribute('disabled');
      stickyAddButtonText.textContent = window.variantStrings.addToCart;
    }
  }
    
 
 
 Instruction Step 5: Now go to main-product.liquid and search </product-info> paste the render code as shown in the video
 
 
 {% render 'sticky-atc-custom', block: block, product: product, product_form_id: product_form_id, section_id: section.id %}
  
  
  
  
Instruction Step 6: If you want to keep updating the data of variant when changing them multiple times add this line of code in updateURL() and please follow the video to do it correctly
  
  
   location.reload();