STYRKR CEL50 promo

A tiered offer that native Shopify discounts could not express, rebuilt as a single Shopify Function.

Role: Developer

Year: 2026

Problem

A tiered offer (15% off 2 boxes, plus a free matching gel at 3) failed with native discounts, because Shopify applies only one product discount per cart and the 15% silently disappeared.

What I built

A single Shopify Function
The buy box stamps a line-item property, and the Function applies both tiers on the server
All pricing is enforced server-side, so adding the free gel by URL without the boxes just charges full price

Stack

Shopify Functions, JavaScript, Liquid, Admin GraphQL

Outcome

Shipped July 2026 after testing all four flavour combinations on a duplicate theme

What I learned

Never trust the browser with a price.

More work

Network design: Multi-subnet network designed and built in Cisco Packet Tracer
Phishing simulation: A Gophish campaign in a lab, from landing page to tracking
Checkout race condition: A time-of-check/time-of-use issue in a Shopify checkout flow
Wargames & labs: OverTheWire, TryHackMe and PortSwigger Web Security Academy
Charlie Oven store: Running the Shopify store for a British outdoor oven maker
Charlie Oven HQ: Internal operations panel for orders, shipping and factory paperwork
3D kitchen configurator: Plan an outdoor kitchen in 3D, then buy it on Shopify
Stockist: B2B wholesale app for Shopify
STYRKR CEL50 promo: A Shopify Function in place of native discounts
STYRKR ERP & automation: NetSuite through Celigo, plus n8n for staff on- and offboarding