tomodachi

Problem

Most wellness apps fail. Not because they’re poorly designed, but because they use the wrong motivational model — surveillance, streaks, and shame. They extract attention rather than serve wellbeing. You miss a day and a red broken streak tells you you’ve failed. You keep a streak and feel anxious about losing it.

The behavior change literature (BJ Fogg, in particular) points to something different: small, immediate feedback loops tied to things you already care about work far better than punishment-based systems.

Process

The starting hypothesis was the Tomodachi Effect: people form genuine emotional bonds with digital creatures, and those bonds change their behavior. If you care about the pet, you care for yourself.

Built as a macro-HCI prototype proposal with Mai Al Shaaban for Professor Dylan Cashman’s HCI course at Brandeis.

Hardware constraints shaped every design decision. The 240×240 circular display is beautiful but small — pixel art was the right visual language. Magnetic attachment meant no permanent commitment; you clip it somewhere that makes sense for your day.

The hardest lesson: unchecked assumptions cost hours. I assumed the GC9A01 display had capacitive touch built in. It didn’t — the touch layer is a separate component (CST816S) that needed its own integration. Building hardware means working backwards from what the system is actually doing, with no error logs to guide you.

The enclosure went through three printed iterations — each one tighter against the manufacturer STEP files, each one smaller than the last.

Solution

A clip-on wearable device featuring:

Circular 240×240 color touchscreen — pixel-art pet and environment rendered via TFT_eSPI
Touch input — tap and swipe gestures via the CST816S gesture recognizer
Haptic feedback — ambient vibration reminders via the Adafruit DRV2605, without pulling you out of what you’re doing
Magnetic attachment — N52 neodymium disc magnets snap to a clip, wristband, or bag strap
500mAh LiPo + USB-C charging — all-day battery, no proprietary cables
3D-printed PLA enclosure — ~35–40mm diameter, modeled in Blender

The Tomodachi Effect in practice: when you log self-care (sleep, water, focus breaks), the pet thrives — its environment brightens, it moves differently. When you skip it, the pet shows it. No streaks, no shame. Just a creature you care about.

Problem

Process

Solution

Links