Ok first question,
I found a new strat that pretty much allows you on impossible mode to do the skips that were only possible with easy-hard mode since there's a hp difference. You pretty much flick your mouse back and forth and shoot to get more momentum while in slow mode and you can use it to 100% prevent damage depending on how well you speed up or slow down. With this, lvl 27 and 28 skips are 100% possible and etc. Asking this because you can pretty much go as high as you want provided you have energy (time stop). This applies to any mode too I guess.
There's also another strat I saw for lvl 38 which was just to tab infinitely between both Marine and Proxy to lag out the enemies. Ironically that "glitch" looks pretty unreliable and seems slower than my strat, but that's one example. Although pretty unfun imo, I assume it's all fair game in what you find for glitches as well as long as it's NLS (No Level Skipping) at least.
Second Question, are you allowed to buy from proxy's shop before timer starts or sell her guns? If you're wondering how this is possible, you can tab in the game while in the lvl menu and the game just highlights to the next button. Idk why Eric added that but I assume it was for accessibility reasons. Anyway, that's a cool thing I just found out and was wondering if I can go into Proxy's shop. Even anywhere in the run really if I wanted to buy anything for her shop before it was unlocked too is another question I had.
Last Question, are browser runs taken into consideration? I don't play browser since it actually is worse to play on than flash file for this game from what I tested. This is kinda related to my 2nd point because you can only tab in the flash game for proxy's shop before you unlock her shop. I mean, I saw no one here post their run being on the H5 version. The reason I'm asking this is because there's a big difference between flash version with wall clipping on 60 fps and the fact that's it's just too smooth. Therefore, making it quite unreliable in that factor when doing certain skips in general. All the runs here have been flash so I guess it wouldn't change the rules unless there's a new category for it because the browser has limitations which make it worse for Speedrunning.
