This achievement is a lot easier than it sound.
It's one of my first tries and there is a lot of mistakes, but the ten billions are easy to reach thanks to the Ice Palace.
Some quick advices:
- Be Patient.
- Power up when you kill boss, it's a lot of suicide bullets.
- Watch replay and train to learn boss paterns.
- Be familiar with 1.1 controls.
- Use power up as soon as you can.
- Watch your back, suicide bullets can appear right behind you.
- Get used to spot lethal bullets from suicide ones so you can dodge them.
I chose Sakura because her two familiars give a wider suicide bullet absorption area, but I think that Windia is a good choice too.
You know you can change the controls and it won't mess up the achievements right? I changed my familiar control to the right stick on pretty much every version of the game ( MBL, 1.1 Arcade and 360)
OZZYRULES200 8 months ago