I used to have this via a CD.
Surprisingly, it is a fusion of turn based strategy, platformer and mini games. The objective is to acquire all the ingredients Getafix needs for a new elixir of his.
The key levels that are required to unlock the ingredients are platformer levels that need to be completed either as Astérix or Obélix. They require defeating a certain number of enemies and sometimes beating a boss.
The catch? Julius Caesar will be sending his Roman legionaries to re-conquer the territories you've claimed. Should a region with a special ingredient fall to the Romans, you have no choice but to complete the level again. And of course, should the Gaulish village ever fall, it's Game Over.
Actually I never managed to complete it, but overall it's a fun little game.