Why it's on the list: Portal is amazing, and I wanted to justify my recent unnecessary purchase of the Xbox 360 version of The Orange Box - by getting some sweet Achievements.

How I played it: On my Xbox One via Xbox 360 Backwards Compatibility, with an Orange Box disc.

When I played it: October 2016

How far I got:

Finished the game
105/175 Achievement Points (out of 1000 in The Orange Box)
Finished a handful of challenge maps

What I thought:

The first time I played Portal - the first time I played any Valve game, actually - was on a trip with my friend Jack up to his relatives' farm. We played as much of The Orange Box as we could between learning to drive, watching sheep get drenched, and shooting empty bottles with a .22 rifle. GlaDOS' dialogue and the intriguing puzzle design propelled us all the way through Portal.

This game remains one of the tightest puzzle game experiences ever. It has a hilarious, black sense of humour and the puzzles are almost beautiful in their elegance. I still think Portal 2 is my favourite of the two, but we'll see once I get to it - there's something really appealing about how this first game takes a simple concept and does so much with it. Outside of the main story, the challenge rooms get too hard for their own good, relying on pixel-perfect coordination rather than lightbulb-moment puzzle solving. Everyone should play Portal, though - it's one of the closest things to a perfect video game.

The Checklist