# Holo (ホロ)

> Google's design language for Android, introduced with 3.0 and pushed so hard that carrying it unmodified became a compatibility requirement for every 4.0 device. It rules a black ground with hairlines and lets a single cyan blue carry selection, focus and progress. It arrived as a guarantee as much as a look, since an app that asked for the theme by name would be drawn the same way even on a phone wearing a manufacturer's skin.

- IndexStyle No.514 — https://indexstyle.org/styles/holo
- Kind: Style · Family: Google UI · Era: 2011–2014
- Mood: Technology, Futurism, Calm
- Color cues: #000000 / #33B5E5 / #F3F3F3 (cues taken from reference works, not a fixed palette)

## Defining characteristics

- White text on black, with sections divided by one pixel hairlines instead of filled panels
- A single cyan blue at #33B5E5 lighting only selection, the underline of a text field, and progress
- A full width action bar pinned to the top, and a strip of Back, Home and Recents keys at the bottom
- Tab labels and list section headers set in bold, all uppercase

## Best used for

- Recreating an Android app screen from roughly 2011 to 2013 with the period's actual widgets and theme names
- Building hierarchy in a dark admin screen from hairlines and one accent color, without adding panels or shadows

## Composition recipe

- Typography & lettering: One geometric leaning sans across the whole interface, in two weights only. Tabs and section headers go uppercase with the tracking opened slightly.
- Layout & structure: A full width action bar is fixed at the top and a single column list fills the space under it. Sections are separated by hairlines rather than white space, and a strip is reserved at the bottom for the navigation keys.
- Material & texture: Ground is black or a pale #F3F3F3, text is white or dark gray, and rules are one pixel of white at reduced opacity. Restrict the accent to #33B5E5 alone and let it glow only on press, selection and progress.

## What to avoid

Redrawing the widgets so they no longer inherit from the theme throws away the one thing this style buys you, which is looking identical across devices, and leaves your app the odd one out on a skinned phone.

## Application checklist

Before calling a piece an application of this style, check it against the defining characteristics:

- [ ] White text on black, with sections divided by one pixel hairlines instead of filled panels
- [ ] A single cyan blue at #33B5E5 lighting only selection, the underline of a text field, and progress
- [ ] A full width action bar pinned to the top, and a strip of Back, Home and Recents keys at the bottom
- [ ] Tab labels and list section headers set in bold, all uppercase
- [ ] At least one reference work below has been studied directly
- [ ] The caution above ("What to avoid") has been addressed

## Related styles

- **Material Design (マテリアルデザイン)** — A design system that reduces the physical metaphor of paper and ink to rules of shadow and overlap. Elements are given elevation, shadow states the hierarchy, and motion carries physical cause and effect. It became the model for UI design being distributed as a system. → https://indexstyle.org/styles/material-design
- **Metro (メトロ)** — Windows Phone's flat language, which cast type rather than icons in the lead role. Large typography, flat-color live tiles and layouts that run off the edge of the screen transplanted the clarity of transit signage into UI, opening the flat era ahead of iOS 7. → https://indexstyle.org/styles/metro

## Further study

- Android 4.0 の互換性定義文書が無改変の主題をどう義務づけたか
- Theme.Holo と DeviceDefault を分けた理由と、両者の使い分け
- Roboto が高解像度画面向けに作られた経緯と、その字形の特徴

## Reference works

- Android 4.0 のホーム画面（Galaxy Nexus）2011 — Wikimedia Commons / CC BY 2.5 — https://commons.wikimedia.org/wiki/File:Android%204.0.png
- Android 4.1 のロック画面（Galaxy Nexus）2012 — Wikimedia Commons / CC BY 2.5 — https://commons.wikimedia.org/wiki/File:Android%204.1%20lockscreen%20on%20Galaxy%20Nexus%2020120712.jpg
- Android 4.3 の警報ダイアログと一覧画面 2014 — Wikimedia Commons / Public domain — https://commons.wikimedia.org/wiki/File:Screenshot-of-CMAS-test-dialogue-19-Feb-2014.png

## Source of record

- Android Developers Blog — Holo Everywhere (2012年1月) — https://android-developers.googleblog.com/2012/01/holo-everywhere.html

## Machine surfaces

- JSON: https://indexstyle.org/api/styles/holo
- Image-generation prompt (legally clean): https://indexstyle.org/styles/holo/prompt.txt
- MCP: https://indexstyle.org/mcp (tools: search_styles, get_style, compose_styles; prompts: image-prompt, apply-style)