Duo is a flagship theme for CS-Cart and Multi-Vendor 4.17.2 to 4.21.x, a child of Responsive, so every add-on keeps working. From 1024 px the page splits in two: a fixed context panel on the left (campaign slides on the homepage, the category image, the product's images, the vendor's logo and story) and the shop on the right. Phones get the panel as a picture at the top. Eight two-tone schemes, serif display type, lookbook rows and three home layouts: Duo, Story and Classic.
One design, eight two-tone schemes
Duo is one design. Each scheme is a pair: a shop ground and a panel colour, set as Theme Editor colours. Open any of them in the live demo.
Shoppers always see what they are buying: product images stay in view beside the buy box, category pages keep the category picture and subcategories next to the products, and filters run as a bar above the grid. Deal timers count down to the real end of your promotions. Every scheme keeps text contrast at 4.5:1 or more, controls are at least 44 px tall, motion stops for visitors who prefer it. No visitor data in the page: safe for the 4.21 full page cache.
How it works
Install the zip in Add-ons, activate Duo in Website > Themes and pick a scheme. The first admin page after activation adds the demo catalogue once (your own products are never changed) and fills the home blocks. The panel fills itself from your category and product images; the homepage slides are a normal HTML block. Switch layouts in Design > Layouts. Licence: one production domain, 12 months of updates; staging and local copies are free. Without a valid licence the store shows the standard Responsive look and keeps selling.
Features
Split-screen frame from 1024 px: fixed context panel left, shop right; full width on cart, checkout and account pages
Context panel per page: campaign slides, category image + subcategories, product images (scroll, arrow keys, zoom), vendor store
Eight two-tone colour schemes (6 light, 2 dark) with checked text contrast, editable in the Theme Editor
Three home layouts: Duo, Story (numbered department chapters) and Classic (no split)
Installs with full demo content: every section and demo products are ready after activation
Lookbook row "The edit": a scene with three numbered pieces and their products
Serif display type, numbered sections, open product cards on tinted image wells
Sticky header, mobile bottom bar, swipe gallery, filter sheet and sticky buy bar on phones
Deal timers from real promotion end dates
Demo technology store installed once on activation
Multi-Vendor ready: seller lines on cards, vendor store in the panel
Tested on CS-Cart and Multi-Vendor 4.17.2; templates compiled with Smarty 5 against 4.21.2; PHP 7.4 to 8.3
Duo next to our other flagship themes
Every Kavio theme has its own character. Duo is the split-screen one: a fixed image panel beside the shop.
Theme
Character
Pick it when
Duo
Split screen from 1024 px: a fixed context panel (campaign slides, category image, the product’s own images, vendor store) beside the scrolling shop; two-tone schemes and serif display type
your products sell on their pictures and you want the look of a brand flagship store
Campaign store: flash bar, sticker badges, dark deal zones, story circles
your store runs on flash sales and weekend drops
What you get
Package
kv_theme_duo-1.0.0.zip: the theme and its wrapper add-on, installed through Add-ons → Manage add-ons. Activate it in Website → Themes, then pick a colour scheme in Website → Themes.
Editions
CS-Cart, CS-Cart Ultimate, Multi-Vendor and Multi-Vendor Ultimate 4.17.2 – 4.21.x, one package. A child theme of Responsive: no core files are changed and add-on templates keep working.
Updates & support
12 months included. Updates keep the theme files you changed; your layouts are never replaced.
License
1 production installation; subdomains, staging, dev and localhost are free. The theme checks its license for your domain once a day from the admin panel. Without a valid license the storefront shows the standard Responsive look instead of the Duo design; cart, checkout and orders keep working. How licensing works
Compatibility
We list only the builds we install and test on. “Tested” means the full test plan was run on that build; “Supported” means the build is inside the supported range and uses the same hooks.
CS-Cart version and edition compatibility
CS-Cart version
CS-Cart
CS-Cart Ultimate
Multi-Vendor
Multi-Vendor Ultimate
4.22 and later
Testing next
Testing next
Testing next
Testing next
4.21.2
Supported
Supported
Supported
Supported
4.20.x
Supported
Supported
Supported
Supported
4.19.x
Supported
Supported
Supported
Supported
4.18.x
Supported
Supported
Supported
Supported
4.17.2
Tested
Supported
Tested
Supported
Before 4.17.2
Not supported
Not supported
Not supported
Not supported
Last tested build: CS-Cart 4.17.2, Nov 7, 2026Tested on: CS-Cart 4.17.2, Multi-Vendor 4.17.2
Requirements
Platform
CS-Cart, CS-Cart Ultimate, Multi-Vendor or Multi-Vendor Ultimate 4.17.2 – 4.21.x
Requirement
Administrator access to the admin panel
Core changes
None. Hooks and template overrides only
1.0.0
Nov 7, 2026
Latest
Added 7
Duo theme (child of Responsive, kit 1.2.8) for CS-Cart, CS-Cart Ultimate, Multi-Vendor and Multi-Vendor Ultimate 4.17.2 - 4.21.x.
Split-screen frame from 1024 px (kit shell "split"): fixed context panel on the left, the shop on the right; cart,
Eight two-tone colour schemes (Linen, Sage, Coast, Blush, Citrus, Lilac, Noir, Tide), text contrast 4.5:1 or more.
Three home layouts: Duo, Story home (numbered department chapters), Classic home (no split).
Lookbook row "The edit", numbered sections, serif display type (Playfair, Epilogue; OFL).
Technology demo store "Twofold" installed once on activation.
Tested on CS-Cart 4.17.2, Multi-Vendor 4.17.2. First release.
Does Duo work with my add-ons?
Yes. Duo is a child of the standard Responsive theme and does not override product, cart or checkout templates, so add-on hooks keep working. Kavio Labs add-ons are styled to match each scheme.
Does it work on CS-Cart and on Multi-Vendor?
Yes, one package for both (CS-Cart, CS-Cart Ultimate, Multi-Vendor and Multi-Vendor Ultimate). On Multi-Vendor it adds the seller line on cards and shows the vendor store (logo, name, description) in the context panel.
What does the split change on wide screens?
From 1024 px, on pages with the context panel: - Product pages show the product pictures in the panel; the stock gallery stays in the page for option images and badges but its pictures are not shown twice. Products with videos (CS-Cart 4.21 product videos) keep the stock gallery in the right half as well, so videos play as usual. Quick view windows always use the stock gallery. - The previous / next product links next to the breadcrumbs are hidden. - The sidebar column of category and vendor pages (filters, category tree, other sidebox blocks) runs full width above the products; filters are laid out as columns. "Recently viewed" is hidden there (it stays on other pages). - Below 1024 px every page is the standard layout with the panel as a picture at the top.
Can I turn the split off?
Yes. Make Classic home the default layout in Design → Layouts: no page uses the split then. To keep it on the homepage only, disable the first grid (the context panel) of the category and product pages in the Duo layout.
Why does a category show a large letter instead of a picture?
The category has no image. Add one in Products → Categories → the category → Images; product shots on a transparent or white background look best on the panel colour.
Why does a product show no countdown?
Countdowns only appear for catalog promotions with an end date. Duo never shows invented timers.
What happens without a licence?
A new installation works for 14 days. After that, without a valid licence, the storefront shows the standard Responsive look; cart, checkout and orders keep working and visitors see no message. The admin panel tells you why and how to fix it. See Configuration.
Does the theme work on my staging copy?
Yes. Subdomains of your licensed domain and local development hosts are covered by the same licence.
What happens if your licence server is down?
Nothing visible: the theme keeps the last verified result and keeps working for 14 days while it retries.
Will an update overwrite my changes?
No. Files you changed are kept (a notice lists them), and layouts and blocks are never replaced.
A campaign-driven theme: flash bar, bento hero with a live deal tile, flash-deals zone with countdowns, sticker discounts and promo cells inside your product grids.
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