Riff Calendar vs Black Hole Sandbox
A side-by-side comparison built from both listings. Blank cells mean the company has not given that detail; we never guess.
Riff Calendar compared with Black Hole Sandbox
| Detail | 
Riff Calendar | 
Black Hole Sandbox |
|---|
| What it does | The calendar you zoom
| A realistic black hole, in your pocket
|
|---|
| Stage | Startup
| Not given
|
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| Founded | 2026
| Not given
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| Based in | SE
| Not given
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| Pricing model | Freemium
| Free
|
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| Pricing | Three weeks free, then $1.99 per month, $19.99 per year, or $39.99 once for lifetime access. Other currencies follow Apple's tiers.
| Not given
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| Key features | - Zoom from half a year to individual days hour by hour
- Create events by holding a free slot and typing
- Reschedule events on the calendar while viewing surrounding events
- Weather forecasts displayed by date and hour
- Daylight indicator showing sunset and sunrise
- Auto-suggest recurring events from calendar history
- Home Screen and Lock Screen widgets at multiple sizes
- Works directly with iCloud, Google, and Exchange calendars
- Round times by default with option for exact times
- Time zones and reminders
| - Real-time ray tracing through curved spacetime
- Augmented reality view of black hole
- 37 color palettes and custom colors
- Customizable accretion disc textures
- Emoji swarm replacement for accretion disc
- Upload custom photos to accretion disc
- Interactive orbit and zoom controls
- Save custom presets
|
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| What makes it different | - One continuous calendar with no separate views instead of switching between month, week, and day screens
- Direct editing on the calendar itself rather than in hidden forms
- No server, account, or data collection
- Works with existing calendars, no import needed
- Paper-like simplicity with digital power
| - Scientifically accurate simulation using general relativity equations
- Real-time physics applied to personal photos and emojis
- Blend between realistic and impossible designs
- Watch lensing effects on your actual room in AR
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| Community votes | 0 | 0 |
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| DR (Domain Rating by Ahrefs) | 2 ● no change since last check | 23 ▼ −1 (down) since last check |
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| Trust Flow (Majestic) | 7 | 0 |
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| Citation Flow (Majestic) | 14 | 21 |
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| Referring domains (Majestic) | 20 | 12 |
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4 details filled in for both companies.
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