Super Juice

Technical decisions

1. 01

   Native, not web

   The environment is a bar: wet hands, no signal in the cellar, opened in the middle of service. Kotlin with Jetpack Compose gives an instant cold start and works fully offline — the app requests zero permissions and makes zero network calls.

2. 02

   Formulas tested against the source

   The factors come from Kevin Kos's official calculator. Rather than trust the transcription, unit tests compare the app's output against the exact source values, decimal by decimal. In an app whose only job is to calculate, the test is the product.

3. 03

   Language chosen in-app, not inherited from the system

   Fruit names aren't direct translations: what English calls Lemon and Lime are 'limão siciliano' and 'limão tahiti' in Brazil — and 'lima' in Portuguese names a different fruit entirely. Letting the user pick PT, EN or ES inside the app removes ambiguity in a field where the wrong fruit means the wrong recipe.

4. 04

   Minimal persistence with Room

   The last five recipes, reloadable with one tap. No account, no cloud, no sync — data is born and dies on the device, which removes a privacy policy, a backend and a recurring bill in one decision.

Screens

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  Home screen: fruit picker and peel weight input

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  Result for 100 g of peels, with a copy button

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  Grapefruit adds MSG — each fruit has its own formula

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  History of the last five recipes, reloadable with one tap

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  Dark theme, with amber accents

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  The same app in Spanish — language is chosen inside the app

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  Language picker: Portuguese, English and Spanish