Marketing ROI Simulator, Darwani Works

Marketing ROI Simulator

A standalone, zero-dependency marketing budget simulator for a boutique European marketing agency. It captures visitor intent through a GDPR-compliant lead gate and models Meta & Google advertising performance by combining industry benchmarks with real campaign historical data. Every submission is piped to an n8n automation engine that updates a Google Sheets cockpit and instantly fires email alerts to the sales team.

Vanilla JSn8nGA4 APIGoogle SheetsWix Embed

Scattered benchmarks and a leak-heavy lead funnel.

The agency wanted an interactive lead magnet on their Wix-hosted site where prospective clients could model advertising returns in their specific sector (Hospitality, Construction, B2B, etc.). The challenge was three-fold: the widget had to be lightweight and single-file to bypass Wix's strict iframe limits, it had to model multi-stage marketing funnels (Meta Ads and Google Search clicks) using actual historical data from 50+ managed client campaigns, and it needed to capture and route lead events instantly to the sales team without risking data loss or exposing backend operational logic.

The solution

Lightweight Vanilla UI and a Token-Isolated n8n Webhook.

I built the widget as a self-contained, single-file HTML/CSS/JS application with zero dependencies to ensure 100+ Lighthouse scores and instant loading within Wix Classic embeds. Instead of direct API access on Wix or exposing sensitive tokens, the widget communicates with a self-hosted n8n webhook. When a user submits the GDPR-compliant lead form, n8n writes the data to a Google Sheets database, handles duplicate events via UUIDs, and triggers an email notification to the sales team only when the user requests a follow-up. An 'internal mode' (via URL parameters) allows agency representatives to skip the gate for live pitches.

From simulation to warm lead.

Goal & Sector selection

Visitor selects one of 4 marketing goals (Awareness, Traffic, Leads, Recruitment) and one of 15 sectors.

Budget & Mix

Visitor sets a monthly budget and drags a single slider to adjust the Meta / Google Ads split.

Lead gate submission

Visitor fills in contact details. n8n stores the lead in Google Sheets and tags the event as lead_aangemaakt.

Performance projection

Widget renders expected reach, clicks, CPL, and monthly leads growth on a dynamic chart.

Sales notification

Visitor can request a follow-up meeting. If clicked, n8n flags the lead in Google Sheets and instantly alerts the sales team by email.

The moving parts.

Realistic Sector BenchmarkingModels CPC, CTR, and CPL across 15 distinct business sectors (Hospitality, Construction, B2B, etc.) by blending industry benchmarks with real client campaign data.

GDPR-Compliant Lead GateForces a lead submission (name, company, email, phone) before rendering the simulation results, serving as a primary conversion tool.

Interactive Channel-Mix SliderAllows users to adjust their budget allocation between Meta Ads and Google Ads using a unified, responsive single-slider that keeps the total at exactly 100%.

Dynamic Spline ChartingDisplays projected lead/traffic/reach growth over 6 months using a custom SVG cardinal spline area chart with micro-animations and interactive tooltips.

Internal Sales ModeUnlocks an internal benchmark panel showing database details (Google CPC/CTR, Meta CPM, sales cycle, and UUID) and allows agency representatives to skip the lead gate using a secret URL parameter.

n8n Webhook PipelineAutomatically pipes data to a Google Sheet and triggers email alerts to the sales team whenever a client submits a form or requests a follow-up meeting, using deduplicated event tracking.

How it's built.

Vanilla JS / CSS

Used for maximum flexibility, instant page speed (Lighthouse performance >95), and zero build-step overhead within the Wix iframe.

n8n

The integration engine, hosting the webhook endpoint that receives lead data and orchestrates database updates and sales notifications.

Google Sheets

Serves as the lead storage ledger, giving the sales team a transparent, read-only dashboard of all prospects.

Google Analytics (GA4)

Pushes dataLayer events (simulator_gestart, lead_verzonden, meeting_gevraagd) to a Google Tag Manager container inside the iframe for accurate campaign tracking.

How the pieces connect.

Lightweight frontend widget connected to n8n for database storage and instant notifications. Here is the data flow.

Wix Website EmbedWix Iframe

embedded inside Wix, the widget processes the simulation locally and captures visitor data

Marketing ROI SimulatorVanilla JS / CSS

posts the lead JSON payload to a self-hosted n8n webhook, protecting API tokens from the browser

n8n WebhookIntegration Spine

n8n records the lead in Google Sheets and fires an email alert to the sales team if a follow-up meeting is requested

Google SheetsLead Database

Sales Mailbox (Gmail)Agent Notification

Who it's for.

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Marketing agenciesAgencies looking for a high-converting, interactive lead magnet to capture warm prospects.

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Low-overhead dev projectsWeb widgets that must load instantly inside restrictive CMS environments like Wix, Squarespace, or Webflow.

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Data-driven sales teamsTeams who want to demo campaign projections on the fly using real historical data.