# Castle Defender vs Microbe Explorer

The clearest difference is in-app purchases: Microbe Explorer at none against Castle Defender's 1. Microbe Explorer also leads on update cadence (every 4 weeks vs every 26 months) and iOS requirement (11.0 vs 15.0). On price, ads and device support there is nothing between them.

Both are free to download. Castle Defender sells 1 one-off in-app purchase. Microbe Explorer asks for nothing beyond the download.

Castle Defender ships an update every 26 months, Microbe Explorer every 4 weeks. The most recent releases landed on October 8, 2026 and October 1, 2026 respectively.

## The numbers

| Metric | Castle Defender | Microbe Explorer |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (2 ratings)](https://appshunter.io/ios/app/castle-defender-machine-gun3d/id1580943009/reviews)** | — |
| Number of ratings | **2** | — |
| In-app purchases | Yes | **No** |
| Ads | Yes | Yes |
| Update frequency | Every 26 months | **Every 4 weeks** |
| Monetization | Free with in-app purchases | — |
| Size | 215 MB | 126 MB |
| Requires iOS | 15.0 | **11.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 17+ | 4+ |
| Developer | [Maysalward UK](https://appshunter.io/developer/1241753360) | [Adknown](https://appshunter.io/developer/1243054661) |

## What reviewers say

### Castle Defender

[App page](https://appshunter.io/ios/app/castle-defender-machine-gun3d/id1580943009)

Defend your town from relentless skeleton armies in this arcade shooting tower defense game. Upgrade weapons and defenses to survive increasing waves and defeat the undead boss. Shoot your way through the hordes to protect the city and its people.

**Highlights:** Wave-based skeleton defense, Weapon and defense upgrades, Boss battles, Arcade shooting gameplay, Town protection

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Remove Ads | $3.99 | one-time |


### Microbe Explorer

[App page](https://appshunter.io/ios/app/microbe-explorer/id1636308114)

**In-app purchases:** none


## Frequently asked questions

### Is Castle Defender free?

Castle Defender is free to download, with in-app purchases available.

### Is Microbe Explorer free?

Microbe Explorer is free to download, with no in-app purchases.

### Do Castle Defender or Microbe Explorer have ads?

Both Castle Defender and Microbe Explorer show ads.

### Which is updated more often, Castle Defender or Microbe Explorer?

Castle Defender ships an update every 26 months, and Microbe Explorer every 4 weeks. Most recently, Castle Defender was updated on October 8, 2026 and Microbe Explorer on October 1, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*