After the slow beginning things really do open up immensely. The levels are split into groups of three or four mines located in the same sector of space. Each of these groups is thematically consistent, so you face similar graphical styles, robots, secret bits, tricks and so forth. Beyond the first few you'll discover the water worlds. You start out in a fairly nondescript little room. Open the door though, and you'll find yourself at the top of an enormous pit with running water way down at the bottom. I'm not sure how I can properly explain the dimensions of this room - I guess it takes about five seconds to fly to the opposite wall and a bit longer to reach the pool down below - but I can guarantee that your eyes will widen significantly the first time you see it. Then you'll fly through the gap on the side wall and find yourself at the top of another room of equally enormous proportions there too.

After you've destroyed all the robots here (I'll just gloss over that, I'm still concentrating on the architecture)you will undoubtedly want to know where all that water is coming from. Glide downwards to the water's surface and you will notice it appearing from a cave at one end and running into another cave at the other end. Exploring in either direction will mean encountering narrow twisting tunnels, small canals cut through the floor of larger rooms, waterfalls and complete darkness. The last two together make for a particularly scary combination. Picture it, you've just finished off a nasty missile-bearing robot, but in doing so you've shot out the only lights along the cavern. Firing off a couple of flares will briefly light the way ahead, indicating a towering waterfall. Soon the flares fade and all that registers on your senses is the overwhelming roar of the rushing water. One of D2's new features is the inclusion of a headlight power-up, which will come to your aid in situations like this. It does, however, drain your energy reserve quickly, so use it sparingly. Often the game looks better without it anyway - spooky shadows and frightening dark corners, you know.

Later on there are the lava worlds. One of several especially memorable incidents from these occurs when you duck through a doorway and find yourself in a fragile cage above a powerful lava flow. The cage acts as a kind of bridge across the deadly lava, but venturing from the safety of the doorway will leave the half dozen or so robots on either side. Attempting to blast them from within the cage is futile, so your best bet is to use the new afterburner function to dart across then try to find another route into these rooms. Eventually you will, but not before steering through some of the most breath-taking scenes you've ever seen in a game. Think swooping between incredibly big, oddly structured rooms with deep red, glowing walls and blindingly bright orange lava floors and flows, packed with mechanical spiders billowing fireballs and hooded orange creatures bombarding you with ricocheting Phoenix cannon death.

Better still, some of the lava flows look a bit strange, as if you can almost see through them. Crash into these and you'll appear on the other side, opening up more caves, robots, and usually the odd secret room as well. The same thing happens in the water levels. Many of the waterfalls can be flown through, though some cheat a bit by looking exactly like normal impenetrable waterfalls. Occasionally you'll find yourself being shot at by something you can't see, if so then then offending robot is probably hiding behind that not-so-solid wall behind you. Or else it's invisible. Eeek!