Even or Odd 1
Every incoming enemy in this free-to-play action roguelite from Fermat Freaks co., Ltd fires a number at you, and your only permitted responses are two: teleport to the upper lane if it is even, the lower lane if it is odd. That single classification rule, lifted from the Collatz Conjecture — a real unsolved problem in mathematics — is the reflex test the entire game is built on.
Players control Ichi, an amnesiac magical girl, ascending floors against a constant barrage of magic numbers. Reading a digit correctly lets you charge and return the shot; chaining correct answers multiplies damage output, and driving an enemy’s number all the way down to one triggers a finisher. A separate timing system rewards striking projectiles back at precisely the right moment, functioning as a parry that can reverse difficult bullet-hell situations, with an auto-parry available as a fallback when the screen becomes unmanageable.
- Two-lane teleportation mapped directly to even/odd classification
- Combo multipliers that scale with consecutive correct reads
- Finisher attacks triggered when an enemy number collapses to one
- Manual and auto-parry options for deflecting incoming fire
- Over ten equippable Grimoires that modify Ichi’s abilities
- Ninety achievements across nine categories including combo ceilings, floor records, and damage peaks
Between runs, collected currency flows into permanent stat upgrades, and Grimoires — magic books each carrying distinct effects — are discovered and slotted to shape how future attempts play out. The combination of reflexive lane-switching and Grimoire loadout decisions gives runs a character beyond raw number-reading speed. The game released on June 28, 2026. Players who enjoy rhythm and pattern-recognition games but want a structural reason to keep climbing — and who don’t mind a light narrative mystery threading through the action — will find the Collatz framing genuinely earns its presence rather than sitting as a cosmetic skin.
