As I said recently (and for the umpteenth time), freedom was a big part of the original Deus Ex - perhaps the most important ingredient of all. The developers of Human Revolution have clearly strived to emulate this, allowing the player great leeway in terms of how they approach a given situation. At the most basic level, you'll invariably be able to creep past foes or engage them in full-on combat. Even within this binary choice there's a sublevel of options: do you taser the guards or tranquilise them from afar, or else time your movements so that you avoid them altogether? If you're taking a more violent approach, do you snipe them, close in and shoot them with a silenced pistol, or simply dash in and blow your foes away with a shotgun?
All of the above are viable approaches, although it must be said that straight combat is no easy matter. Human Revolution may look and feel like a standard FPS at times, but the action takes no prisoners. Gunplay is entirely skill-based, rather than being determined by Fallout 3-style hidden dice rolls, but "going Rambo" is a suicidal tactic on anything but the lowest difficulty setting. Even with the help of a contemporary recharging health setup, a handful of bullets are all it takes to end your life.
If you're determined to launch an all-out assault on your foes, the best tactic is to hole yourself up in a corridor or room with one entrance, and to pick off the opposition one at a time. While the AI is smart enough not to simply stand in the open, foes are generally still happy to come to you - even if it means entering a killzone that slaughtered their buddies a few moments ago. While the shooter elements in Deus Ex work perfectly well, there's no doubt that the raw action is at its best when you're taking a quieter approach - tasering watchmen and dragging their bodies out of sight, or waiting for the perfect moment to crawl through a busy room. At moments like this, the game recalls the spirit of Metal Gear Solid - high praise indeed for any stealth outing.
While there's a bevy of nice upgrades for your weapons - explosive rounds for your shotgun, and a mod that shows exactly where your crossbow bolt will land - there's no doubt that the best toys on offer are those that are attached to Jensen himself. Earn enough XP and you'll unlock a Praxis point, a valuable currency that can be used to open up new tools and weapons on the electronic Swiss army knife that passes for Jensen's body. However you're choosing to play, there's definitely something on the skill tree that'll prove invaluable - allowing you to see through walls, lob about heavy in-game objects, or even turn invisible. Since some of these powers will open up otherwise inaccessible paths to your objectives, early-game upgrades can often leave you with a gnawing dilemma.
Sadly - or perhaps happily, depending on your outlook - this indecision doesn't last long. While there's no shortage of sexy new tricks on offer, it's surprisingly easy to fill up the tree. Up until now Eidos Montreal has insisted that you won't be able to get everything in the course of a single playthrough. While that's technically true, you'll certainly get all the augmentations that you really want. If you're doing all the side quests on offer you'll collect XP with surprising speed, and you can find a limited number of Praxis kits on sale, or even just lying around if you look hard enough.
Beyond this, you eventually realise there are one or two upgrades that are far more useful than the others. While there's been lots of coverage of the fact that Jensen can learn to punch through walls, killing the hapless enemy on the other side, you're only able to do this at specific points in the world, which are comparatively scarce. You'd do far better to invest your points in X-ray vision or the aforementioned cloaking ability, both of which prove invaluable under any circumstance. There are a few skills (or even entire branches) that you really don't need, and once this becomes apparent the whole upgrade process loses a little of its former sheen. The original Deus Ex forced you into either/or choices, preventing you from taking all the best powers on a single playthrough, and it would have been great if Eidos Montreal had followed suit here.
In terms of general play, however, it's endlessly gratifying to know that there's usually an alternative solution to the problems at hand. It's a shame that the game forces you into a boss fight every so often, because elsewhere you're completely free to avoid combat altogether. While the build-up to these encounters is usually handed well, showcasing some of the most visually creative environments in the story, they still feel like a design hiccup in a game that's otherwise content to let you play the way you want. If you've been avoiding combat, the first of these battles may prove particularly challenging (and annoyingly reliant on a gaming cliché that I won't reveal here). Subsequent boss fights will present fewer issues - partly because you'll be expecting trouble, and partly because you'll have a better selection of tricks up your sleeve.