You don't have much health when going through the time loop trying to fix it, so staying on top of all the ways to heal yourself is paramount to your success. Deathloop is a game of slow things, research and crafting. one master plan, but one mistake, and it could all be over.
Deathloop uses the Dishonored health mechanic. If you take damage, your health is highlighted, and you can recover what's lost by finding cover and waiting for it - your health will start to recover, but not entirely. But if you take damage when your health is highlighted, you'll lose whatever is highlighted, and then some.
You have ways beyond expectation and natural recovery. You can find Fiz-Pop bottles in homes and around the world that will instantly heal you when used. Additionally, there are health stations that will fully heal you, but they are limited and impractical to find in the most difficult situations.
The last thing that can heal you is certain trinkets, but those won't instantly heal you, like Fiz-Pop. Rather, they are buffs to help your healing needs, like regen life faster or heal a bit more when using Fiz-Pops.
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