EVEN OR ODD 1: Reflex-Based Action RPG Tackles the Collatz Conjecture

8/21/2026, 8:49:26 PM

Release date: 6/28/2026

Tags: #rpg #action #action-rpg #roguelike #action-roguelike #casual #strategy #2d

User Reviews

Score: 67%3 user reviews
Review Count: 3 reviews
Fetched At: 8/21/2026, 8:49:26 PM

Reference prices

Japan

Free to Play (JPY)

Steam JP

Free to Play (USD)

Steam

Live Store Snapshot

Body text may reflect the state at publication time. For the latest sale, price, and review changes, prioritize the live price panel, review panel, and the Steam store listing.

Japan Price: Free to Play
Global Price: Free to Play
Sale Status: Regular pricing
Price Checked At: 8/21/2026, 8:45:24 PM

Key highlight

EVEN OR ODD 1 is a free-to-play 2D action RPG where players battle mathematical enigmas using pure reflexes. Master lane-switching to hit even or odd numbers in this unique take on the Collatz Conjecture, released June 2

Who this is for

For a truly unique gaming experience that blends mathematical puzzles with high-speed action, EVEN OR ODD 1 is a must-try. This free-to-play title will test your reflexes and strategy, keeping you hooked.

🖥️ Hardware Guide for Comfortable Play

Based on the game's recommended specs, showing a comfortable performance target and example parts (PassMark reference)

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CPU

Game's recommended spec

Intel Core i5 / AMD Ryzen 5

Comfortable play target

15,600 pts(~130% above spec of 12,000 pts)

Parts near this range

Intel Core Ultra 5 32215,587 pts ARM - 12 Core 0 MHz15,636 pts Intel Core i3-1220PE15,664 pts

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GPU

Game's recommended spec

DirectX 12 compatible GPU (2GB VRAM)

No PassMark data — please check the manufacturer's site

* Scores are reference values. Actual performance varies by in-game settings, resolution, and system environment.

Build a PC to match this performance → BTO Guide

Details

Overview

EVEN OR ODD 1 is a free-to-play action RPG developed and published by Fermat Freaks co., Ltd. This unique title challenges players to confront the famously complex Collatz Conjecture through sheer reflexes and quick thinking. Players step into the shoes of "Ichi," a magical girl who battles relentless monsters firing "Magic Numbers." The core gameplay revolves around instantly teleporting between lanes – the upper lane for even numbers and the lower lane for odd numbers – to read incoming digits, charge shots, and smash them back before they overwhelm you. It's an extreme reflex battle where a single misstep can be fatal, pushing players to their limits as they try to unravel this mathematical enigma.

Highlights

Unique Mathematical Challenge: The game centers around the Collatz Conjecture, offering a brain-bending puzzle wrapped in fast-paced action.
Action RPG Roguelike Elements: Combining RPG progression with roguelike challenges and intense 2D action, players will need to master quick reflexes and strategic lane-switching.
Free-to-Play Accessibility: Available for free on Steam, EVEN OR ODD 1 invites a wide audience to experience its distinctive gameplay loop.

Who It's For

This game is perfect for players who enjoy fast-paced action games that also offer a mental challenge. If you're intrigued by unique concepts, mathematical puzzles, or action RPGs with roguelike elements, EVEN OR ODD 1 might be exactly what you're looking for. It appeals to those who appreciate games that demand quick reflexes and split-second decision-making.