You can get the achievement without much effort, when you get lucky with the level selection.
Pick Rayar (the woman) as your character and play through the first level. If the second level is anything other than the stoneage level, restart the mode. If you get into the level, play until you reach the miniboss. Stay at the right side of the screen and you can shoot the spawning enemys above you. Stay at the line of sand and earth, to collect the coins of the enemys. Whenever the enemies on the left start running at you, evade them by going down and up again when they passed. When you reach the score points just die or quit out.
Alternativly you can just play through the story and abuse the save system, so you dont die so often. Set the time to 29min 59sec in the option to get more timescore.
You can also use this trick to get the achievements from other modes.