Surprised!ReactionTimeChecker? vs Mental Dice
Price, ratings, monetisation and update history for both apps, side by side โ with what reviewers say about each.
Surprised!ReactionTimeChecker?
This app captures photos of users when they are startled by sudden fear images. It's designed for playful pranks to surprise friends and family, documenting their genuine reactions. Note that it utilizes sound effects even in silent mode and requires camera permissions.
- Sudden fear image display
- Captures user's surprised photo
- Sound effects in silent mode
- Requires camera permission
- Prank and surprise friends
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This app " Surprised! Reaction Time Checker?โ is not an app to measure reflexes. When playing in a game that measures reflexes, it suddenly displays a fear image, and it is a surprise app to take a picture of the player of that moment. Surprise your friends, lovers and family and get their photos! You may get a photo of the surprised look of a yearning person ... *This application has sound effects even in silent mode. *In order to use the camera function to take photos, you need "Camera" and "Add photos only" permission to use this app. *Please check the photos taken with the "Photos" app. *Shaking the device violently can cause photos to be blurred. *Be aware that the player is surprised and may break the device. *Even if the user uses this game, the user or a third party other than the user, equipment, or even if there is a case where damage or a failure has occurred in human relations, we do not have any responsibility. *If you are using iOS 14.5 or later, a dialog asking for tracking permission will be displayed at the first startup. Production: NSC, K.K. If you have any problems or requests, please check the contents of the โContact Usโ page on our website and send us an e-mail. Click here for โContact Usโ: https://www.nscnet.jp/inquiry.html
Mental Dice
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This is an application for performing magic tricks. You can let the opponent choose the dice roll freely, and you can secretly know the dice roll selected by the opponent. Please check "How To Use" after launching the app.
Screenshots
Verdict
The clearest difference is price: Surprised!ReactionTimeChecker? at Free against Mental Dice's $3.99. Surprised!ReactionTimeChecker? also leads on update cadence (every 6 months vs every 26 months) and device support (3 vs 1). Mental Dice's advantage is ads (none vs shown). On in-app purchases and iOS requirement there is nothing between them.
Scored on Price ยท Rating ยท Positive reviews ยท Number of ratings ยท Update frequency ยท Ads ยท In-app purchases ยท Monetization ยท Best chart rank ยท Devices ยท Requires iOS
Surprised!ReactionTimeChecker? is free to download; Mental Dice costs $3.99 up front. Neither carries in-app purchases, so what you see is what you pay.
Surprised!ReactionTimeChecker? ships an update every 6 months, Mental Dice every 26 months. The most recent releases landed on June 1, 2026 and September 21, 2026 respectively.
| Parameter | Surprised!ReactionTimeChecker? | Mental Dice |
|---|---|---|
| Price | Free โ better | $3.99 |
| Positive reviews | 100.0% of reviews | โ |
| Update frequency | Every 6 months โ better | Every 26 months |
| Ads | Yes | No โ better |
| In-app purchases | No | No |
| Monetization | Ad-supported | โ |
| Devices | iPhone, iPad, iPod โ better | iPhone |
| Requires iOS | 15.6 โ better | 16.0 |
| Further details โ not scored | ||
| Size | 24 MB | 1 MB |
| Age rating | 12+ | 17+ |
| Developer | NSC, K.K. | matsumoto yuuki |
In-app purchases
Surprised!ReactionTimeChecker?
No in-app purchases
Mental Dice
No in-app purchases
Questions
Is Surprised!ReactionTimeChecker? free?
Is Mental Dice free?
Do Surprised!ReactionTimeChecker? or Mental Dice have ads?
Which is updated more often, Surprised!ReactionTimeChecker? or Mental Dice?
Other comparisons
