Tiny Bridge Achievement in Vampire Survivors

Refer to Greatest Jubilee (50G) for unlocking Inverse mode. That needs to be done first before this achievement can be attempted.

Once you unlock Inverse mode, all stages have an option to turn on Inverse mode when you start them. Inverse mode, in addition to mirroring the level vertically, gives all enemies 200% health, +5% health each minute, and +1% movement speed every two minutes. Note that the vertical mirroring of a level is purely visual; the items that would be present in a level are still in their normal locations, not in mirrored locations.

As you might suspect, this mode will make things a little tougher, since enemies are stronger and get stronger as you progress. However, with a proper build, there won't be much of a noticeable difference at all when playing in Inverse mode. Before attempting this, it should go without saying that you already have all the permanent stat boosts purchased. The character you play as doesn't make a huge difference, but in terms of normal characters, Pugnala is a great choice since she gets +1% Might per level, which really helps offset the increase in enemy health. As for builds, you should always go with the standard evolved Santa Water, evolved King Bible, and evolved Axes. Since Gallo Tower is a close quarters level with lots of walls, the evolved Rune Tracer is great. Additionally, the Song of Mana, even if not evolved, is great for a vertical level like this. If you don't want to evolve the Song of Mana, then at least grab the Spinach so its damage increase helps offset the extra enemy health even further. For a sixth weapon, I'd recommend the evolved Lightning Ring just because the Duplicator you use with it is so good for all weapons you have.

Once you get that build going, you shouldn't have any issues getting to level 80. I do recommend being as aggressive as possible though, in the hopes that you can reach level 80 before the 25 minute mark, because the crab boss will have a huge amount of health in Inverse mode. That, coupled with Blue Death, can make the end of the stage pretty intense. If you stay aggressive, you could reach level 80 before the boss though.