Interface Essential

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Front End Developer Tool Dart

<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

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## 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

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## Brand & Cultural Identity

### What it communicates

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

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## 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.

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## 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

Logo

Flutter Logo icon - Core Duo Set

Download Flutter Logo 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.