We wanted to do something slightly different with the rally genre. Colin's great, WRC's great, but we wanted something that kind of reflected the more technical side of rallying, the kind of simulation aspect.

VARIABLE, DYNAMIC WEATHER on stages, so the conditions are diffierent every time you play! Holes in the road will slowly fill with water when it begins raining.
 
VARIABLE TIME OF DAY on stages, depending on when it's your turn to drive the stage, and the start times are different every time you play -- sometimes a stage might be a day stage, sometimes it might be a night stage.
 
VARIABLE SURFACE CONDITIONS based on how many cars have run the stage ahead of you (in you're first out on gravel stage, you suffer what the real drivers must suffer).

"We've modelled some sections to be more worn than others, and if you can get your front tyre on that section, if you can hook it in, the reduced friction can actually slide the car round - it's something you see all the time in rallies, but nobody's doing anything like that in games."
 
Physics
 
"Rather than using a single-bodied physics system, which most other rally games do, we've gone for a multi-body physics system where we're simulating what is essentially a real car chassis, the McPherson struts, all of the stuff that you'd expect to find in a complicated car modelling piece of software. We've written a complete car simulation, similar to something that professionals would use in the car industry when testing all the initial concept ideas. So we're simulating quite a lot of the interior of the car, the engine, the way the combustion cycle works, we're modelling things like the temperature of the brake fluid and the oil and the water from the radiator, so if you get a puncture in the radiator that has a knock-on effect on your engine, as it would in real life. When you drive through big puddles in our game, water can actually enter the cooling vent on the car, which does have an effect on how the car fires up the cylinders."
 
Damage model  
 
"We've got this system whereby if you crash into a tree, your car might be damaged beyond repair, but if you can carry on you can get back onto the stage. If you're near spectators they'll give you a push and push you back onto the road, or if you roll the car they'll push you back over. But it kind of creates this whole scary thing: you're doing well in the championship, you're in the lead - how hard do you push on the stage? Do you go for the win again, or do you go for the second place knowing that you'll retain your lead in the championship? You've invested so much in the race, and you don't want to screw it up; you want to be first. If you roll the car down a side of a mountain, it's helicopter rescue time - no respawning."