As you get score, the game will 'evolve' giving you more weapons, levels and difficulties to be selected. Once you have unlocked the 'Field' weapon, play Bonus Level 1-4. Collect the power ups as quickly as you can and then simply move from side to side to hit as many shapes as you can. 10,000,000 will be easy and you'l also get the achievement for 1500 chains if you haven't already got it. The achievement(s) won't pop until it's game over so don't quit.
Here's a video by SuperWhammyBar which may help: -