The reason people were getting such high scores on Physics was that previously you could continuously get shrink rays meaning your multiplier went insanely high. They patched it though so you can't shrink more than 4/5 times.
I kept waiting for a good weekly challenge but eventually got sick and so tried to do it properly. Managed on my first try on Aquarium Survival. The room # probably doesn't matter as it's the same basic idea:
- Nothing chases you so you don't have to go fast if you don't want to. You can actually slow down and take your time for the whole thing. I wouldn't recommend it for the entire level, but the vast majority of the time it helps to manoeuvre around obstacles.
- The pearls with base multiplier are worth 1000 points. That means a lot less corn to collect. Best way I found to get them was to hold down on the screen (so that you're falling as slowly as possible) and wait for the clam to open, then quickly move towards and away to get it.
- Ensure that every time you see a death finger power up you collect it and go crazy shooting at things. 50 points per obstacle destroyed is a pretty decent amount.
- If you feel confident with power downs activated then collect them. It always helps if you already have a decent multiplier when you come across a pearl or death finger, but don't go too crazy. Bubbled corn and hypnofish aren't much hassle, but collecting too many shrimp will cause you great problems if you come to a tight gap. Also, if you see any power downs when you're going for a pearl or have death finger activated, try to collect them. And of course, if you're going for power downs avoid antidotes.
- Save your corn magnets and bathspheres. I generally used a corn magnet when I had death finger activated and at least an 8x multiplier. As for the bathspheres, they're good if you come across a section that you've died at least twice on, or if you feel death finger is going to get you killed. Activating it will protect you from a few obstacles if you miss them with death finger.
- As tempting as it may be, don't use a bathsphere when you collect an indestructoid. It's difficult to get the bathsphere to spin enough times and make it worth your while. Instead, collect the indestructoids and hope for a death finger and some power downs.
- Perhaps an obvious one, but avoid the anchors as they will more than likely drag you straight into an obstacle.
- Don't chase the squids for points. They'll make you go too fast and more than likely lost a life.
- Keep in mind that the yellow jellyfish aren't deadly, they only make you lose 50 points. Avoid them if possible, but if it's a choice between one of those and something that will lose you a life it's clear which route to choose.
- Something else to avoid are red 'rapids'. These will make you speed up far too much so try to keep away. Conversely, green rapids slow you down so can actually be very helpful, unless there is a rotating fish below. If that's the case, use a speed up to get past.
- The most obvious of all is to collect corn as long as doing so doesn't put you in danger. Every point helps.
- And finally, try not to lose more than 1 life per section. This again is quite obvious, but if you do I would recommend ignoring the above tips and just concentrating on collecting a couple of more lives.
Following this it took me roughly an hour an a half to get the achievement. You can also press the home button to take a break as when you load the game up again it will allow you to continue.
I hope this helps