Yes. The Door System is free and complete: knob doors, a locked door that needs a key and a keypad door, with the demo scene and the source.

Can I buy one system on its own?

The systems are now sold as one collection with three tiers. The $7.99 tier has the five systems most games need; $14.99 unlocks all ten.

Which Unity version do I need?

Unity 6 (6000.3) or newer with the Universal Render Pipeline (URP) and the Input System package, which new Unity 6 projects already include. Needed tags and layers are created on import.

Do I get the source code?

Yes. Every script ships as full C# source with comments, so you can read it, change it and extend it.

Can I use these systems in a commercial game?

Yes. The code and the original low poly art can be used in your games, commercial ones included. You can't resell the system itself.

Yes. The systems are versioned on itch.io and updates are free: download the newest file from your itch.io library.

10 Game Systems for Unity: Doors, Inventory, Save, Shop & RPG

Ten drop-in gameplay systems for Unity 6, each with a demo scene, a README and C# source: doors, inventory, save and load, shop, character customizer, starter RPG, elevator, fracture, replay and traffic. Start with the free Door System.

Freepaid editions from $7.99Download free on itch.io

Checkout on itch.io · instant download · free updates

The free edition is a full download, not a demo. Pay for a paid edition on the same itch.io page to unlock more, and follow Imersa Studios there to get new kits.

Specs
Editions	Free / $7.99 Standard / $14.99 Complete
Engine	Unity 6 (6000.3) or newer
Render pipeline	URP
Source	Full C# source with comments
License	Commercial use allowed

Features

Free: the complete Door System (knob, key-locked and keypad doors)
Standard ($7.99): Door, Inventory, Save & Load, Shop and Character Customizer
Complete ($14.99): all 10 systems and the demo hub that launches every scene
One folder per system: scene, scripts, prefabs and README together
Short, commented C# you can read in an evening

What’s in the download

10 systems: Door, Inventory, Save & Load, Shop, Character Customizer, Starter RPG, Elevator, Fracturer, Replay, Traffic
A demo scene per system and a demo hub (Complete)
Full C# source code with comments
Original low poly art you can use in commercial games