In Original Mode, the main aim is to get your Break Rate high so you get more points for killing enemies. It increases more quickly in Break Mode and faster still in Double Break. Also, below the Break Rate you have your multiplier. This is maxed out at x4.8 in non-break mode, x5.6 in Break Mode and x6.4 in Double Break Mode. The multiplier is activated by holding down the lock-on shot and locking on to as many enemies as possible.
If you get the x6.4 multiplier just before a section with lots of enemies, you can get the timer on the multiplier to shoot up, sometimes up to 1000 or 2000. It's therefore possible to link separate Break Modes while still having x6.4 multiplier. (This is easier to do with Type Z ship, especially on Stages 4 and 5). It would look something like:
Lock-on attack > x4.8 multiplier > Break Mode> Lock-on x5.6> Double Break > Lock-on x6.4 > Screen full of stars!
The trick is to know when to activate Break Mode in order to hit the parts when most enemies appear.
As for the extends; in Simple Mode I usually collect the Item Bonus. This gives you 1 million for Stage 1, 2 million for Stage 2, etc. If you collect it in Stages 1-4 that's worth at least 10 million, so it's worth going for the Item rather than the Extend. In Original Mode I usually just go for the Extend. Picking up the energy means you'll be able to enter Break Mode more quickly, but it's not that big a deal.
One other thing, if you max out your lives count (up to 9) then in Original Mode you get the choice of Item or Energy at the end of the stage. I managed to do this once in Stage 4, so the Item gave me a 4 billion score bonus. Sadly, I still didn't manage to clear Stage 5.
