How the game is built

TenkaiClassOnline is built by one developer, from scratch, since August 2025.

The game

• Engine: Unreal Engine 5.7, written in C++20. Blueprints are kept as thin wrappers; game logic lives in C++.
• Online from day one: one dedicated server runs a single shared world. No client is ever trusted with game state: combat, inventory, movement checks and death all resolve on the server, and clients send input and display results.
• Progression core: the rules that grow attributes and resolve classes live in a standalone C++ module with no engine dependencies. It was checked step by step against a Python simulator, which is also the balancing tool. The progression model page describes it in full.
• Test bots: automated bots run the progression loop on their own, so long-term class growth can be tested without weeks of manual play.
• Saves: each character is an Unreal SaveGame slot per account (TCO_Save_<account>_Slot<n>.sav), versioned and migrated field by field on load.

This website

• A static site built with Astro, in English and Italian.
• Game data, not hand-typed numbers: a read-only exporter runs inside the Unreal editor and writes the data tables (items, creatures, mounts, pets, abilities, regions) and renders (item icons, creature portraits, the world map) to files. A sync script validates them, together with the class tables, and the site is rebuilt from that snapshot. Class, world, bestiary and item pages come from it, and so do the combat formula weights.
• Character profiles: the profile page reads a .sav file entirely in your browser. It parses Unreal’s binary save format and never uploads the file. Accounts on the site are a local demo for now: they live in your browser’s storage.