Recently released on Steam, Aperture Tag rests somewhere between a substantial mod, DLC, and a full game release. It uses Portal 2's assets and and setting, but takes one if its mechanics – the use of the blue and orange gel – to create a completely original experience forcing you to examine Portal puzzles in a whole new way.

Instead of using the portal gun to make your way through Aperture's labs, players have a new paint gun letting them fire off the speed-boosting and bouncing gel nearly anywhere.

The game is the brainchild of Eugenio Roman – a dedicated modder of Valve's games – who decided to step up his tinkering to create a full experience with Aperture Tag. We spoke with Roman about building the game, how involved Valve was with the project, and how the game came to life.

Correct me if I'm wrong, but the ability for players to paint the walls with the blue and orange gels from a gun, as you do in Aperture Tag, was supposed to be part of Portal 2 at one point, right? Valve cut the mechanic. What made you decide it was worth exploring?

Eugenio Roman: I am not exactly sure about this. There is a weapon_paintgun in the files, and as an entity in the Portal 2 level editor, but it doesn't do anything. So certainly they had plans to do a paint gun, but it looks like it got cut out of the game.

The story for Aperture Tag starts way back before Portal 2 was released. In my wait for Portal 2, the new gel mechanics where shown and in the announcement they said the gels came from the team behind TAG The Power of Paint, who were hired by Valve. I downloaded TAG immediately and I had a ton of fun playing that game. TAG was very short. It’s only about 7 maps, and when I finished it, it left me wanting more. For about a year or more I had this taste in my mouth about wanting to create maps for a paint gun.

Almost three years ago I found this video and asked the creator (who I knew from the Portal 2 mapping community) if he was going to use his device to create maps, he said no and I asked if I could use it and he gave it to me. After some changes to the gun's logic and behavior I released a map to (The Workshop was not available for Portal 2 yet). The level was highly praised, even though the gun was extremely unresponsive. It was great fun, and I knew this was valuable and definitely worth exploring.

A bit of time goes by and I am lucky to be in the closed beta for the Perpetual Testing Initiative. There I had the chance to meet some Valve employees and after some discussions, I inquired about a paint gun. I mentioned that all that was needed was a working entity (the previous weapon_paintgun) and I said the community would make the maps.  When I learned that wasn't going to happen, I decided to take matters into my own hands. I built some extra levels, but nothing too serious. I started beta testing the Left 4 Dead 2 workshop and the Counter Strike: GO (CSGO) workshop and the CSGO one was taking more of my time. I entered the first CEVO/GameBanana contest for CSGO in early 2013. I worked hard for about 3 months on a single map and in the end, the contest left a bad taste in my mouth. When maps that obviously violated the rules didn't get taken out, I decided that was the end of contests for me.

I returned back to the paint gun and had to think what I would do. I could release the maps in episodes or just create a full modification of the game. I decided a modification would be the best path, as it would allow me to keep editing the first levels based on new experiences and changes made to the gameplay as the game progressed.

In May 2013 I wanted to visit Valve, so I bought a plane ticket and visited. I had planned a day for Valve and the other to explore Seattle, but to my surprise they brought me in the for two days. I talked about my visit on Reddit along and posted some pictures. That visit was a huge confidence booster and from there I started dedicating basically all my free time to Aperture Tag. By the end of 2013, I already had all the campaign mapped out. It wasn't pretty, but it was playable. I made something that I enjoyed playing and the project just grew bigger and bigger.

The Pneumatic Diversity vents/tubes used to travel from location to location – wasn't that a feature ultimately cut from Portal 2, as well?

From what I recall from the first trailers, the Pneumatic Diversity Vents were supposed to suck through the portals. You could portal near a turret and it would get sucked through. I am not sure why they were cut in the end. I think the vacuum tubes just didn't have that much diversity in them as a testing element. In the final game there is a Vacuum Ride where the player and Wheatley get sucked through.

Before Portal 2, I had played through Portal many times over, and I always found the elevators very slow. In Portal 2, the elevators were much better, but I still had this predisposition to think they were too slow. Which is why I decided to use Vacuum Tubes in Aperture Tag, to make it feel much faster.

For more on how the game was built and how long it took, head to page two.