Overview
Built around the concept of "Your day, in a single number," TENSU is an iOS app that lets you score and record how your day went on a scale of 0 to 100. How many points was today?—You answer that question with just a single number. This small habit, finished in seconds, gradually visualizes the biorhythm of your days. It was released on the App Store on May 12, 2026.
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Background of the Development
TENSU grew out of a habit the developer kept during his university days: giving himself a score out of 100 every day.
It started casually and continued casually, but as the days went on, it brought many discoveries.
- Patterns by day of the week emerge
The average score is low on Mondays and high on Saturdays, for example—a biorhythm within the week becomes visible.
- The behaviors that raise and lower your score surface
High-scoring days and low-scoring days each share certain behaviors in common. What raises your score, and conversely what brings it down? A daily reflection arises naturally.
- The three-month average was almost exactly 50
Life is said to have its ups and downs, but the highs and lows balance out. Once you see that, you can forgive yourself a little on the low days.
Above all, the very act of giving a score leads you to pause once and look back on the day. The contours of days that rush by in a blur come back into focus a little—we turned that experience into a single app.
If diagrams make the structure of things visible, then TENSU visualizes the rhythm of your own days. The simple act of compressing a day into a single number brings more insight than you might expect. With an approach characteristic of ZUKAI, we aimed to create a small pause in everyday life.
This is our third app developed using generative AI, following "PACE" and "hajimete." From design and UI to implementation, the entire process was completed solely through dialogue with generative AI—we advanced development through Japanese-language exchanges alone, without writing code directly. This time we ventured into server-side implementation for the first time, trying out a new structure of one-time purchase plus anonymous server linkage.
Highlights
◾️Score today in "5 seconds"
To record, you simply pick today's score from a 21-step palette in increments of 5 points. Even without adding any text, you can easily record today's score.
◾️Look back with the calendar
Each day's score accumulates as color on the calendar.Even if you don't remember the numbers, you can visually look back on the flow of a month or a year.
◾️Your own rhythm comes into view
Because you can look back on your scores and their reasons in chronological order, you can see weekly and monthly averages and differences, and your own rhythm comes into view.
◾️See everyone's recent trends
Only scores, age groups, and regions are aggregated anonymously, letting you glance at the daily scores others have recorded. This is a screen not for comparison, but for feeling that you are not alone.
◾️No ads, one-time purchase, no login required
It's a one-time purchase with no additional charges and no login required. Your records are saved on your device, so you can use it as a quiet journal that is yours alone.
App Information
App name: TENSU
Supported OS: iOS
Release date: May 12, 2026
Languages: Japanese / English
Developer: Tetsuro Kondo