Have a Heart

Have a Heart is Challenge #25. Isaac begins the challenge with Charm of the Vampire and 12 heart containers, but only one of them filled. The goal is to defeat Mom's Heart or It Lives.

Difficulty

Charm of the Vampire is the main way to fill Isaac's heart containers (see below for exceptions). All red heart pickups are replaced with pennies (half heart = one penny, full heart = 1+1 free penny). HP up items (e.g.: Breakfast) give red heart containers, but do not fill HP. The Lovers Card spawns coins instead of red hearts. The 2 of Hearts card and Yum Heart have no effect. The Tick will still reduce a boss' health, but will not heal upon entering the boss room. Shops sell coins instead of hearts. Slot machines, blood donation machines, the Hematemesis pill, and any of the beggars drop coins instead of hearts. Even a Super Secret Room which usually contains hearts will contain money instead. It is also impossible to recover health with Pyromaniac, Placenta, or Leech.

Strategy

The biggest difficulty lies in acquiring health. However, with numerous heart containers, there are several strategies to survive the challenge. First is finding a way to heal red heart damage.

The Full Health pill is a major boon for this challenge.
- The Bad Trip pill can also heal fully, but only when at half a heart.
- When combined with these pills, the Placebo becomes very powerful. It can be purchased in shops.
XIX - The Sun card also heals to full health, alongside other benefits.
- Combined with a Blank Card, the challenge becomes trivial. This can be purchased from shops.
Obtaining the Habit or Sharp Plug from a shop allows Placebo or Blank Card to be used at will without any fear of death.
Rainbow poop will also give full health, but it is also very rare.
Beds still refill Isaacs' health.
Adrenaline is very helpful as Isaac will have multiple empty heart containers.

Second is getting rid of excess heart containers. Removing even one heart container will make obtaining Deals with the Devil and Angel Rooms much easier, as the open HP spot can hold Soul/Black hearts, providing insurance against red heart damage.

The Devil Room or Black Market deals not only give good items, but also free up space for soul hearts. This, naturally, comes with the downside of preventing Angel Rooms from appearing.
- Abaddon can remove all heart containers to be replaced by six Black Hearts.
The Health Down pill can clear away some extra heart containers to allow picking up Soul/Black Hearts. This can synergize with Placebo nicely.
Guppy's Paw is one of the more useful items for survival, because it removes hard-to-fill heart containers and replaces them with soul hearts.
Potato Peeler can be found in shops and easily removes excess empty heart containers for Cube of Meats, Allowing you to easily get a couple Meat Boys if desired.

A third method involves grinding enemies to replenish Isaac's health.

Mulligans and their variants, Sacks, and other spawning enemies can provide limitless sources of enemies to fully fill health.
Getting the D7 and repeatedly clearing a room filled with easy-to-kill enemies can fill Isaac's entire HP bar.
The Shell Game Beggar can be a useful method of spawning flies.

Because hearts turn into coins, shop purchases are easier to make.

Trinkets such as Bloody Penny, Burnt Penny, Counterfeit Penny, Flat Penny, and Rotten Penny are beneficial, as there is a greater chance of coins dropping when Isaac finishes a room.
Bumbo and Bum Friend are also more beneficial with the increase in coin drops.

Some other things to note:

If Isaac is at full health, the boss should take priority. Health lost during the battle can be replenished from unexplored rooms.
Avoid using Hematemesis, as it will remove all but one heart without spawning two hearts as usual.
If Isaac dies with a 1up!, all heart containers will be filled.
Judas' Shadow purges all heart containers and leaves 2 Black Hearts.
Mom's Locket refills half a heart each time a key is used.