[quote name='freshzen']I played through the game 3 times so far.
Are there any tips for beating the game without continuing? It seems like getting to the final boss without dying isn't too bad but actually beating both of them (especially the last one) its very difficult.[/QUOTE]
If you want to *really* cheap it out, choose level 1 for every stage. Learn the scoring mechanisms (watch some replays) so you can extend your life bar... in Arcade mode you get an extension at 20 million and 45 million points. I usually hit level 3 for the Volcano and Graveyard since a shit ton of points can come from there, but for some people, it might be too much.
Remember that for every bar of life that gets depleted, you get three more bombs. If you defeat Jitterbug without using a bomb, when he dies you get a large cake worth 2 life bars. At this point, I have almost a full 5 bars going into Tyrannosatan, and bomb the shit out of him... 3 bombs per life bar, I usually have 5 bars total... he goes down fast. It's not worth it to hoard your bombs if you think you will get hit, since one bullet takes off one full bar and those 3 bombs are gone forever... ramming an enemy only takes off 1/2 a bar.
When you get to Jitterbug, try to have your counter at 1000 - enter power up mode immediately, and if you are good at dodging his bullets he will go down fast. If you get hit, no worries - you get a large cake (if you remember not to bomb!!) Also, if you can do the Swamp at level 2, the car at the end of the swamp will provide a cake when you blow up if you are running low on life.
Use Rosa. She is probably the strongest one in vanilla arcade.
I've 1cc'ed it with both Rosa and Windia at this point (almost had it with Casper, but
ed up on Jitterbug)... I usually do a combination of Level 1, 2, and 3. I only use Level 1 for stage 2-1 (and whatever stage I choose last, for reasons I'll detail), that Tree Boss can be a bitch. Once you memorize the patterns, it gets real easy.
I also went through the game about 10 or 12 times before I started to go for 1cc's, since it was my first time playing it and I wanted to get a feel for it. I recommend to knock out EVERY other achievement, namely the 8 or so for finishing the game as the characters, before 1cc'ing, so you have an extremely good handle on the game.
Also check out the replays, they can be a huge, huge help if you are a visual learner. I hope this has helped! Let me know if you want me to go more in detail about anything.
My personal combo is usually this - Lakeshore Lv 3, Volcano Lv 3, Halloweentown lv 3, Graveyard lv 3, Forest lv 1, Swamp lv 1... I make sure the last stage I do is lv 1, since it makes the castle that much easier. If you choose level 3 five times, you enter death mode, where everything has suicide bullets, so be weary of that. It's usually why I drop to level 1 after the first 4 stages... I hit my first extend in the Volcano, and based on my playing the second extend by the castle.
Also, do the stages you think will be your hardest at the beginning, just to get them out of your way. But it all boils down to practice, practice, practice especially if you don't play a ton of shmups.
Edit: Since writing this, I can do 4 stages at level 3, the last two at level 2, and the castle on one credit. Highest score now is ~75 Million on 360 mode. I can do better I think, missing a ton of scoring opportunities.