# repsim — A Natural Selection Sim

> Simulated natural selection and evolution game with customizable replicators. (iPhone/iPad app by Van Sanders.)

- Source: https://appshunter.io/ios/app/repsim/id1610235913 (this page in markdown: same URL + `.md`)
- Developer: [Van Sanders](https://appshunter.io/developer/1610165508)
- Category: Games, Education, Simulation
- Price: Free
- Rating: 5.00/5 from 2 App Store ratings
- Age rating: 4+
- Requires: iOS 12.0 · 114 MB
- Languages: English
- Released: 2022-02-17
- Data updated: 2026-06-07
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/repsim/id1610235913/reviews.md

## What is repsim?

Watch simulated life evolve right before your eyes in Repsim!  
 
Natural selection weeds out replicators (reps) that can't compete! Selectively breed or let them fend for themselves to see what emerges. Feed them, cull them, and toss them into each other. Place objects in their tank that you can drag and throw around. There is even a virus that can take over if the tank becomes too crowded!
 
Repsim is not only a fun way to explore natural selection, it's also great as an educational tool for science teachers and students. 
 
~
 
Jam Out! 
 
Repsim features all-original musical tracks. Each track is meant to loop endlessly and set a different mood. Users can skip through a range of tracks as they play, from calming atmospheric music to wacky surf songs. New tracks will be included with every update!
 
~
 
The Simulation

In Repsim, natural selection takes place within a tank of randomly generated replicators called “reps”. Reps are built out of five segment types, distinguished by color:
 
Red: Attack & feed when they hit another rep
Green: Generate health every second
Yellow: Provide movement every 1.25 seconds
Blue: Heal damaged segments
Purple: Allow a rep to breed (reps without purple segments clone themselves)
 
Before a new tank sim is started, the properties of each segment type can be adjusted. For example, you could make red segments do more or less damage. When you’re done adjusting the sim settings, it’s time to fill the tank!
 
When the simulation starts, a tank is filled with reps. 
 
Each rep has a genome that determines the order and orientation of its segments. When replication (self-cloning) or reproduction (breeding) happens, genetic material is passed on to the next generation with a small chance for mutation. When reps with purple parts touch another rep, they combine the other's genome with their own to make a child!
 
Users can save reps in one tank and spawn them in another with new settings. This allows users to see how the same rep behaves and evolves in multiple environments.
 
 
This is just a taste of what you'll see once your sim tank is up and running. There's even more left to discover in the in-app tutorial!

## Key features

- Simulated natural selection
- Customizable replicator traits
- Interactive tank environment
- Genetic mutation and reproduction
- Save and spawn replicators
- Original musical tracks


## Frequently asked questions about repsim

### What is RepSim?

RepSim is a simulation game where you can observe and influence natural selection. You create and manage 'reps' within a tank, allowing them to evolve based on their genetic traits and environmental factors.

### How does natural selection work in RepSim?

Natural selection in Repsim occurs as reps with traits better suited to the environment survive and reproduce, passing those advantageous genes to the next generation. Less adapted reps are weeded out.

### Can I customize the reps in RepSim?

Yes, before starting a simulation, you can adjust the properties of each segment type that makes up a rep, such as attack power or healing rate.

### Does RepSim have multiplayer?

The provided description does not mention multiplayer functionality. RepSim focuses on single-player simulation and observation.

### Is RepSim available on Android devices?

RepSim is currently supported on Mac and iPad, as indicated by the 'supportedDevices' field. Android compatibility is not mentioned.

### How often is RepSim updated?

The app was last updated on 2022-02-18, shortly after its release on 2022-02-17. New musical tracks are planned for inclusion with future updates.

### What is the age rating for RepSim?

RepSim has an age rating of 4+, making it suitable for a wide range of users interested in its simulation and educational aspects.

### Does RepSim have ads?

The provided data does not specify if RepSim contains advertisements. However, it is listed as free with no in-app purchases, suggesting it may be ad-supported or entirely free.

## Version history (last 1 release)

### 1.1 — 2022-02-18

Typos corrected and minor graphic scale adjustments made.

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-07.*