Interface Essential

Business

Images Photography

Money Shopping

Programming

Computer Devices

Phone

Mail

Map Travel

Food Drink

Nature Ecology

Entertainment

Shipping

Culture

Health

Work Education

Artificial Intelligence

Arrows

Streamline 3.0

Ultimate

Core

Flex

Sharp

Plump

Micro

Freehand

Streamline Material

Nova

Cyber

Streamline Vault

Logos

Pixel

Google Material

Tabler

Remix

Feather

Iconoir

Carbon

Solar

Lucide

Brand Logos

Bootstrap

Atlas

Unicons

Ionic Icons

Phosphor

MingCute

Font Awesome

Majesticons

Mynaui

Radix

Heroicons

Flagpack

Book Open 3

Menu Book Fill

Book Flip Next Page

Book Flip Previous Page

Book Flip Previous Page Arrow

Book Open

Logbook

Auto Stories

Book Open Bookmark 1

Open Book

Auto Stories Alt

Auto Stories Alt Fill

Book Book Pages

Local Library Fill

Book Open 2

Book Reading

Book Open 7

<p>Core is timeless, like the Helvetica font or The Beatles. With its minimalist design and neutrality, it can adapt to any layout.&nbsp;The Duo style is perfect for projects that require differentiation between actions, using color to convey meaning effectively. It also allows you to customize the line thickness.&nbsp;All Core Duo icons are designed on a 14px grid with a 1px default stroke and two customizable colors.</p>

Core Duo

**Summary**: Core's two-color system — 1px rounded line with dark periwinkle blue primary and lighter blue secondary, providing colour-based hierarchy in enterprise SaaS and productivity products without full multi-color commitment. The periwinkle blue is softer than Sharp Duo's corporate blue, creating a polished two-tone system that reads as considered rather than cold. The tone signals semantic colour use: "we use colour to convey meaning, not emotion." Best for enterprise SaaS and productivity tools wanting a controlled two-tone icon system, documentation and help centre iconography, and dashboard systems where colour differentiates category or status.

**Last updated**: 2026-04-23

---

## Fit & Recommendation

### Primary use cases

- Enterprise SaaS and productivity tools wanting a polished two-color icon system
- Feature overview pages in business software
- Documentation and help centre iconography
- Products with a brand blue where the duo treatment reflects the palette
- Notification and dashboard systems where icon colour differentiation conveys category or status

---

## Brand & Cultural Identity

### What it communicates

> "We use colour to convey meaning, not emotion."

---

## Visual & Technical Specs

### Visual properties

| Property | Value |
|----------|-------|
| Stroke weight | 1px |
| Fill | None (line only) |
| Corner treatment | Rounded corners |
| Color | Two-color: dark periwinkle blue + lighter blue secondary |

### Emotional Scores

Core Duo is near neutral on warmth leaning slightly cool — the periwinkle blue two-color system is cool but softer than sharp duo equivalents. It is one of the softer sub-styles in the catalog, as the 1px rounded line at the 14px grid remains light and non-aggressive despite the two-color structure. It is somewhat friendly, with the duo system reading as polished and considered rather than warm but not corporate. It is near neutral on playfulness leaning slightly serious — colour differentiation communicates function and hierarchy. On its human↔mechanical character, it is somewhat human-feeling — the two-color system adds systematic quality while rounded geometry retains a human register.

---

## Pairing & Compatibility

### Typography pairing

- **Primary**: Inter — the blue duo system and humanist neutral type share the same functional design values
- **Alternative**: IBM Plex Sans — slightly more structured, appropriate for the slightly formal dual-colour system
- **Body**: Source Sans Pro — clean, readable, supports the two-colour icon structure
- **Avoid**: Serif fonts at body weight, warm rounded display fonts


<p>The Helvetica of icons. Core is stripped to essential form with generous spacing. It's a timeless workhorse for interface design.</p>

Minimal icons

Open Book icon - Core Duo Set

Download Open Book SVG vector or transparent PNG icon in Duo, Minimal, Stroke, Filled, Wireframe style(s) for Sketch and Figma. It belongs to Core Duo vectors SVG collection.