As soon as Impossible Mission II loads up, the improvements are immediate and obvious. The producers clearly went to work on almost every aspect of the original game, polishing, adding and fixing until this sequel was the result.
There are no great changes to the concept; players familiar with the first game will be immediately familiar with the sequel's mix of exploration, puzzling and platforming, there's just more of it this time around. Instead of one complex, Impossible Mission II delivers eight different buildings, separated by code-locked doors. Each of the rooms boasts the familiar blend of platforms and robots, except the layouts are more diverse and challenging, and the robot ranks have been expanded, with the death-ray-spewing tin cans of the original now joined by a variety of different allies, from largely harmless drones which like to mess around with the lifts, to suicidal death machines which grab the player then leap with him into the nearest pit. While the core gameplay hasn't changed too much, there's a bit more in terms of complexity and content in the sequel.
There's even an attempt to rationalise the setting, replacing the generic environments of the first game with rooms that are recognisably used as offices, gymnasiums, sleeping quarters and so on. This is somewhat undermined by the level design however, as the steps, lifts and gaps so central to the game detract from the sense of a realistic living space. Perhaps it's a touch pedantic of me, but the producers have gone to such effort to make the environments appear as if they have actual utility, so it's a tad disappointing that the acrobatic gameplay doesn't support that effort.
The sound is also somewhat underwhelming. While the graphics have had a very noticeable touch-up, reflecting the advances in C64 game visuals made in the four years since the first game, the sound is little different to that of the original, even reusing the classic "Stay a while!" speech sample. Given the groundbreaking effects of the first game, and the fact that the central puzzle of the game is based on manipulation of sound, it's a shame that more wasn't made of this aspect.
Impossible Mission II is a solid update of a classic game, with plenty of worthwhile additions and tweaks, but there's a slight sense that the purity of the game has been lost, that it doesn't need all these bells and whistles when there's such compelling core gameplay. However, that core gameplay is still present in the newer game, and is still just as compelling; the original title is a more immediate and solid gaming experience, but the sequel is more polished, more varied and possibly more fun to play. Take your pick.