10. Somnia (Cryptic Sea) [Windows, freeware]

Somnia is a 3D first-person perspective outing revolving around light and shadows. Each of the puzzles must be completed by flipping between the shadow and the 3D-world. Platforms which seem unreachable are quite easily accessed through 2D shadow platforms.

It's pretty tricky to describe the experience, so we'd recommend to just go and try it. For anyone who can't work out exactly what they're meant to be doing, try standing on a platform and clicking.

9. ASCIIpOrtal (Joseph Larson) [Windows/Mac/Linux, freeware]

In ASCIIpOrtal you can fire up to two portals with your hand-held portal device, then enter through one before coming out of the other for some mind-bending teleportation effect. Some of the puzzles in this 2D remake of Valve's Portal include manipulating switches using blocks, placing portals on the other side of chain links, dodging boulders before they crush you, and avoiding laser fields that will burn your flesh instantly on contact.

Links to binaries for Windows, Mac and Linux operating systems all available from the Cymon's Games site.

8. Evacuation (Ben Foddy) [Flash, freeware]

Evacuation is a game of strategy, quick wits, and explosive decompression. Aliens have invaded your cargo hold, and the only way to get rid of them is to vent them into space.

7. Closure (Tyler Glaiel, Jon Schubbe) [Flash, freeware]

Closure is a unique 2D platformer created by Tyler Glaiel, co-developer of Edmund McMillen's Aether. The game involves using orbs to light up your surroundings, as the entire area is shrouded in complete darkness with each step outside the light most likely a fatal one.

6. Exploit (Gregory Weir) [Flash, freeware]

Exploit is a puzzle game about terrorism through hacking. By using ports to fire packets of data, the object of the game is to break the code and access the root node. Along the way you'll encounter many a hinderance, including blocker nodes, buffers and port keys.

The tutorial is the best place to start, as it explains the gameplay very nicely. Once you understand the core elements to the game, there's a brilliant Story Mode to play through as well as a Challenge Mode. Not only that, once you've managed to beat the 70+ puzzles available, you can even use the Puzzle Editor to create and share your own!

It's a great little game which very early on feels extremely complicated, yet once the solution has been identified, it exposes itself as actually quite a simple set-up which makes you feel rather clever from figuring it out.

5. Opera Omnia (increpare) [Windows/Mac, freeware]

In Opera Omnia you play a state historian who is charged by his politician friend to come up with convenient theories about migration in the past. Basically, you have to think backwards: if people were in this city during a plague, and if plagues reduce population, that means that they had to have had a lot of people in order to survive that plague: thus, plagues actually increase population if you work backwards in time.

The challenge of each level is that you're given something to prove -- such as prove that 300,000 people lived in this city a long time ago -- and you adjust migration patterns that will show how 300,000 people could have lived in that city a long time ago.

The gameplay may be a bit hard to "get" at first, and a lot of the people I've recommended the game to had a hard time wrapping their mind around the concept, but if you do manage to do it you'll find it a clever gameplay mechanic and some interesting challenges unlike most other games. There's also a pretty well-written story over the span of its 20 levels.

4. Boxgame (Sophie Houlden) [Unity, freeware]

Boxgame is a puzzle platformer in which gravity is ruled by big, transparent boxes in the centre of each level. Jumping off a ledge will result in some crazy re-orientation, after which you most likely won't be standing on the same plane anymore.

Which, of course, leads to lots of lovely puzzles. Sophie has clearly put a ton of thought into some of the solutions (especially towards the end) and, while it never gets incredibly taxing, you'll definitely need to use your brain for this one.

3. Use Boxmen (Greg Sergeant) [Flash, freeware]

Use Boxmen is a 2D puzzle platformer with cleverly-designed levels, where players are required to collect a cube in each level to progress. The trick is that certain areas can't be completed without the aid of your friends, who will mimic your moves when called upon to help. Experimentation is half of the fun, while executing your master plan to perfection can be extremely satisfying, although the link to the video walkthrough might be too tempting for players to resist when faced with a challenge that seems insurmountable at first.

2. Continuity (Ragtime Games) [Flash, freeware]

Continuity is a puzzle platformer in which you have to arrange pieces of a level while playing to reach the key that will unlock the exit door. You can switch between sliding tiles and moving your character around at any time, although players won't be allowed to pass from one card to another if the corridors going out of each don't match.

There are roughly thirty levels to figure out in total.

1. Little Wheel (One Click Dog) [Flash, freeware]

Little Wheel is a point-and-click adventure game which tells the story of a community of robots who had their power shut down due to a minor mishap. By chance a guard robot was brought back to life after getting struck by lightning, and it is up to the player to assist our mechanical friend as it tries to restore power back to the city.

Cutscenes are well-animated, puzzles are easy enough to solve without referring to a walkthrough, and all hot spots are marked clearly with either a gray or white circle. The only real fault to be found here is the length of the game, but even that is possibly down to how entertaining it is to play from start to end.

[Got feedback? Reasons to disagree? Post a response and we'll do a special 'best of reader comments' round-up at the end of our chart countdowns.]