Why a Worker? Google Apps Script blocks direct browser requests (CORS). A Cloudflare Worker sits in between — it fetches Apps Script server-side where CORS doesn't apply, then passes the result back to the browser with the correct headers. Takes ~5 minutes to set up once.

Step 1 — Set up the Google Sheet & Apps Script
1a. Open your Google Sheet → add a tab named Counters with row 1 headers: Key | Count
1b. In the Sheet, click Extensions → Apps Script
1c. Paste this code (replace YOUR_SHEET_ID with your Sheet ID from the URL):

function doGet(e) {
  const sheet = SpreadsheetApp.openById('YOUR_SHEET_ID').getSheetByName('Counters');
  const entity = (e.parameter.entity || 'ST').replace(/[^A-Z]/g, '');
  const d = new Date();
  const key = entity + '_' + d.getFullYear() + '_' + (d.getMonth() + 1);

  const data = sheet.getDataRange().getValues();
  let row = -1;
  for (let i = 1; i < data.length; i++) {
    if (data[i][0] === key) { row = i + 1; break; }
  }

  let count;
  if (e.parameter.action === 'peek') {
    count = row > 0 ? parseInt(data[row - 1][1]) + 1 : 1;
  } else {
    if (row > 0) {
      count = parseInt(sheet.getRange(row, 2).getValue()) + 1;
      sheet.getRange(row, 2).setValue(count);
    } else {
      sheet.appendRow([key, 1]);
      count = 1;
    }
  }
  return ContentService.createTextOutput(JSON.stringify({ count: count, key: key }))
    .setMimeType(ContentService.MimeType.JSON);
}

1d. Deploy → New Deployment → Web App → Execute as: Me → Who has access: Anyone → Deploy → copy the Web App URL

Step 2 — Create the Cloudflare Worker (CORS proxy)
2a. Go to dash.cloudflare.com → Workers & Pages → Create → Worker
2b. Give it a name like sejati-counter → click Deploy
2c. Click Edit code → replace everything with this (paste your Apps Script URL on line 1):

const APPS_SCRIPT_URL = 'PASTE_YOUR_APPS_SCRIPT_URL_HERE';

export default {
  async fetch(request) {
    const origin = request.headers.get('Origin') || '*';
    const corsHeaders = {
      'Access-Control-Allow-Origin': origin,
      'Access-Control-Allow-Methods': 'GET, OPTIONS',
      'Access-Control-Allow-Headers': 'Content-Type',
    };

    if (request.method === 'OPTIONS') {
      return new Response(null, { headers: corsHeaders });
    }

    const url = new URL(request.url);
    const target = new URL(APPS_SCRIPT_URL);
    url.searchParams.forEach((v, k) => target.searchParams.set(k, v));

    const resp = await fetch(target.toString(), { redirect: 'follow' });
    const body = await resp.text();

    return new Response(body, {
      status: resp.status,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
    });
  }
};

2d. Click Deploy → copy the Worker URL (looks like sejati-counter.YOUR-SUBDOMAIN.workers.dev)

Step 3 — Paste the Worker URL in the field above and click Test.