Mathijs Vermaat

mathijsvermaat.github.io

TL;DR — Quick links

Page	Live URL
App Blocked Page	https://mathijsvermaat.github.io/app-blocked.html
Monitored App Page	https://mathijsvermaat.github.io/monitored.html
Generic Blocked Page	https://mathijsvermaat.github.io/blocked.html
Sentinel Maturity Assessment Checklist	https://mathijsvermaat.github.io/sentinel-maturity-assessment.html
WisselApp	https://mathijsvermaat.github.io/WisselApp/

Pages

App Blocked Page (app-blocked.html)

Live page: https://mathijsvermaat.github.io/app-blocked.html

A professional user-facing page that displays when access to a restricted application is attempted.

Purpose: Inform users that a specific application (in this case, Gemini) is not allowed in the organization and provide them with approved alternatives.

Features:

• Clear visual indication that access is restricted
• Explanation of why the application is blocked
• Highlighted alternative with direct action button
• Contact guidance for administrators
• Responsive design that works on mobile and desktop
• Professional styling with gradient background

Current Configuration:

• Blocked Application: Google Gemini
• Approved Alternative: Microsoft Copilot with direct URL
• Target URL: https://copilot.microsoft.com

Usage: Navigate to app-blocked.html in your browser to view the page, or integrate it into your web filtering/proxy system to serve when users attempt to access restricted GenAI applications.

Monitored App Page (monitored.html)

Live page: https://mathijsvermaat.github.io/monitored.html

A professional user-facing page that displays when access to a monitored application is attempted.

Purpose: Inform users that a specific application (in this case, Gemini) is not allowed in the organization and provide them with approved alternatives.

Features:

• Clear visual indication that access is restricted
• Explanation of why the application is blocked
• Highlighted alternative with direct action button
• Contact guidance for administrators
• Responsive design that works on mobile and desktop
• Professional styling with gradient background

Current Configuration:

• Blocked Application: Google Gemini
• Approved Alternative: Microsoft Copilot with direct URL
• Target URL: https://copilot.microsoft.com

Usage: Navigate to monitored.html in your browser to view the page, or integrate it into your web filtering/proxy system to serve when users attempt to access restricted GenAI applications.

Generic Blocked Page (blocked.html)

Live page: https://mathijsvermaat.github.io/blocked.html

A generic blocking page for all restricted applications and services.

Purpose: Display a universal access restriction message for any blocked application without mentioning a specific app.

Features:

• Generic access denied message suitable for all applications
• Explanation of organizational policy compliance
• Professional, reusable design
• Responsive layout for all devices
• IT administrator contact guidance

Usage: Configure your web filtering or proxy system to serve blocked.html as the default response when users attempt to access any restricted application. This is the recommended page to use as a general-purpose blocking page.

Sentinel Maturity Assessment Checklist (sentinel-maturity-assessment.html)

Live page: https://mathijsvermaat.github.io/sentinel-maturity-assessment.html

An interactive assessment checklist for the Sentinel Maturity Model. Used during customer engagements to document data connector onboarding, retention configuration, and detection readiness across all tiers.

Purpose: Provide an audit trail of what was checked and configured during a Sentinel deployment assessment, with rationale and comments.

Features:

• Checkboxes per connector, table, retention setting, and validation step
• Comment field per connector section for rationale and notes
• Assessor name, customer name, date, and workspace metadata
• Real-time progress tracking (overall and per connector)
• Collapsible sections per tier and connector
• Export to PDF via browser print
• Export to Excel via SheetJS (structured spreadsheet with all check items and comments)
• Save/Load progress to JSON (resume later or share between assessors)
• Tier 1 fully built, Tier 2/3 prepared for future content
• No backend or server required — fully client-side

Usage: Navigate to https://mathijsvermaat.github.io/sentinel-maturity-assessment.html or open the file locally. Fill in the assessment metadata, work through each connector’s checklist, add comments, and export the results.

WisselApp (WisselApp/)

Live page: https://mathijsvermaat.github.io/WisselApp/

A substitution and playing-time planner for youth football (jeugdvoetbal), delivered as a fully offline Progressive Web App. See WisselApp/README.md for the full Dutch documentation.

Purpose: Help coaches fairly distribute playing time, goalkeeper rotations, and substitutions across matches, with a live match screen that survives screen lock.

Features:

• Player roster (first names only — privacy-friendly)
• Matches per date with configurable format, halves, quarters, and substitution interval
• Goalkeeper-per-quarter selection with suggestions based on historical goalkeeper time
• Fair substitution schedule that accounts for prior playing time across matches
• Live match screen with large clock, current field/bench/goalkeeper, countdown to next substitution, and audible/visual/vibration alarm 30 seconds before and at the moment of switching
• Lock-screen-proof timestamp-based timer (locking the phone does not reset the match)
• Playing-time statistics across all matches
• JSON backup export/import
• Installable as a PWA on iOS and Android, works offline via service worker

Privacy: All data (players, matches, playing time) is stored locally in IndexedDB on the device. No backend, no cloud — the only network traffic is downloading the static app files from GitHub Pages.

Usage: Navigate to https://mathijsvermaat.github.io/WisselApp/ and add it to your home screen (iOS Safari: Share → Add to Home Screen; Android Chrome: menu → Install app).

License

Licensed under the MIT License.

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