See Video Below
This achievement is for scoring 6 billion points in 2X mode.
themegamancave's solution covers most of the important points, but I was still having some problems. I thought I would add some additional pointers I found helpful and included a video for reference. A lot of this is included in themegamancave's solution, but just adding it again for completeness.
- Use Follett as your character. Set lives to 5 and enemy damage to 0 so that you don't have to worry about dying. You will want to play all Fields at level 3 to maximize enemies and points. Also make sure to play the optional Field F before the final one.
- The key is to fill up your bonus counter to 1000/10000 on the bottom left of screen. The counter goes up by collecting the blue bonus items. These items only appear from attacks by your familiar (the little character floating around you).
- Your familiar moves to the opposite side of you when you move (if you move down, your familiar goes to the top of you). When you hold down either the A or B button laser attack, your familiar will be locked into whatever position it is in even when you move. To collect blue items quickly, you need to control your familiar so it is doing a lot of the damage instead of Follett's attack.
- I only used the A and B button attacks and often would lock my familiar above or below me so that I could try to focus its attack on the enemies. This works especially well for large enemies. It also helps to be close to the enemy, so often times I try to hug the far right of the screen if possible
- At 00:55 in the video I get my familiar locked on to the large enemy pretty well and added 5000 to my counter just from him. This allowed me to max out my counter by the middle of the first level.
- Once the counter is maxed, hit the X button to go into power-up mode. While in this mode, blue "suicide bullets" will appear that will home in on you. These bullets will slow down considerably when they get close to you.
- The key to high scores is to watch the tails coming out of these blue bullets. After a bit, the tail will turn yellow and then red. You want to clear these bullets by hitting the X button again when as many as possible have the red tail coming out of them. This will produce a massive amount of purple bonus items that will quickly increase your score. Kind of hard to see the tails in the video, but one of the clearer views is at 02:00.
- Eventually the entire blue bullet will start to turn red and will disappear, so you will want to clear them with the X button before this happens. You will also lose the blue bullets if you get hit, so if you get into a tight spot, it is usually best to just clear them and get what points you can.
- While in power-up mode, the counter will count down from 1000 and will end when it hits 0. One handy trick is to clear a bunch of blue bullets right near the end of the counter (~20-50 left). You will then be able to collect the bonus items from clearing the bullets after the counter runs out, which will give a nice boost to refilling your counter back up to 1000/10000. At 02:00 and 04:15 in the video, I was able to pull this off pretty well and refilled my counter to 1000/5000.
- During boss fights, you just want to focus on refilling your counter so you will be able to go into power-up mode right when you start the next level. Just get your familiar close to the boss and attack with the A or B button.
- During Field C, while in power-up mode, shoot the floating rocks with your familiar to rack up a lot of points. You can also do this to fill up your counter quickly.
- There are other ways to maximize your score, but repeating this basic strategy should be enough to easily get you 6B points. I had about 2.3B after Field C and almost already had 6B by the time I started the last field.
- Below is a video of Fields A-C, which should give you a pretty good idea of the strategy. If you switch quality to 720p, you should be able to see the video clearer.