The Critical Mass technology team is looking for an inspired, motivated, and experienced Senior Developer to join our Communications team for a contract engagement. We are an experience design agency with a focus on the customer, which means that collaboration and precision execution are at the heart of our process. You'll be working on high-visibility campaign and consumer-facing websites where pixel-perfect design execution and responsive optimization are critical to delivering a premium user experience.

PLEASE NOTE – This is a contract position from July 1 – September 25, 2026

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You Will:

• Deliver pixel-perfect front-end implementations that match design comps across all devices and viewport sizes
• Build responsive campaign layouts with modern animation-rich marketing pages using modern HTML, CSS, and JavaScript
• Work on individual components and page sections within robust, complex websites
• Collaborate with Design, UX, and the delivery team to ensure seamless implementation of designs
• Optimize page performance and ensure WCAG accessibility compliance
• Jump into high-velocity production work with minimal onboarding and deliver under tight timelines
• Take ownership of your work and drive solutions proactively with minimal supervision
• Support the team with clear code, documentation, and knowledge sharing

You Have:

• 4+ years demonstrated experience using Vanilla JavaScript
• 5+ years’ experience using HTML5 semantic markup, CSS3, and CSS/SASS preprocessing
• 5+ years building SVG-based animations and responsive consumer-facing websites
• Strong expertise in pixel-perfect design implementation and responsive design across devices
• Full command of Git, the terminal, and modern development fundamentals
• Strong troubleshooting ability and technical analysis skills – including web performance optimization
• Proven ability to jump into projects quickly and deliver quality work under pressure
• Strong communication skills with a self-sufficient, collaborative approach to teamwork
• Fluency with implementing pre-made components from a component library such as Material UI or similar
• Proven knowledge using utility classes, grid classes, and utilizing CSS frameworks such as Bootstrap, Foundation, Materialize, or similar
• Experience with navigating Sketch design files to find font and color styles and dimensions
• Proven track record of delivering production-quality code on high-visibility projects
• Practice or exposure to developing software with Large Language Models (LLMs), including writing and integrating AI-assisted code
• Experience with web animations (CSS and JS) and web animation libraries (GSAP) 

 

Bonus if you Have:

• Capability with Handlebars or other templating engines
• Skill with Webpack or other front-end build system optimization tools
• Experience working in an agency or fast-paced production environment
• Familiarity with design-to-development handoff processes and design systems
• Awareness with the Atlassian suite of tools (JIRA, Bitbucket, Confluence)
• WCAG accessibility expertise