Have a Heart

Have a Heart is challenge #25. Isaac begins the challenge with and 12 Red Heart containers, but only one of them filled. Unlike other challenges, Treasure Rooms and Shops are available. The goal is to defeat Mom's Heart or It Lives.

Difficulty
Charm of the Vampire is the main way to fill Isaac's Red Heart containers (see below for exceptions). All Red Heart pickups are replaced with Pennies (Half Red Heart = Penny, Red Heart (and Blended Heart) = Double Penny, Double Red Heart = Nickel) ( though Blended Hearts can still spawn). HP up items (e.g.: ) give Red Heart containers, but do not fill HP. The card spawns Pennies instead of Red Hearts. The card and  create no effect. The Tick will still reduce a boss's 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 or. This challenge is slightly easier in Repentance, as Charm of the Vampire now gives a small damage up.

Strategy
The biggest difficulty lies in acquiring health. However, with numerous Red 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 one heart or less.
 * When combined with these pills, the becomes very powerful. It can be purchased in Shops.
 * card also heals to full health, alongside other benefits.
 * Combined with a, the challenge becomes trivial. This can be purchased from Shops.
 * 's effect works, granting full health after defeating each floor's boss.
 * Obtaining the or  from a shop allows Placebo or Blank Card to be used at will without any fear of death (though this may not be the case in Repentance due to these items being revamped).
 * Rainbow poop will also give full health, but it is also very rare.
 * has a chance to create Rainbow Poop when Isaac takes damage, thus picking it up can make the challenge substantially easier.
 * Beds still refill Isaac's health.
 * is very helpful, as Isaac will have multiple empty Red Heart containers.
 * Blowing up a Shopkeeper counts as an enemy.
 * Should you happen to get a summon-based boss like The Duke of Flies early, you can use the minions it summons to farm life, potentially giving you the equivalent of a full health pill on an early floor.

Second is getting rid of excess Red Heart containers. Removing even one Red 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.
 * can remove all Red Heart containers to be replaced by six Black Hearts  twelve Black Hearts, assuming no heart containers have been lost prior.
 * The Health Down pill can clear away some extra Red Heart containers to allow picking up Soul/Black Hearts. This can synergize with nicely.
 * is one of the more useful items for survival because it removes hard-to-fill Red Heart containers and replaces them with Soul Hearts.
 * can be found in shops and easily removes excess empty Red Heart containers for s, allowing you to easily get a couple of 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 fill health.
 * Getting the and repeatedly clearing a room filled with easy-to-kill enemies can fill Isaac's entire HP bar.
 * The Shell Game can be a useful method of spawning Attack 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.
 * and 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 drain you to one filled Red Heart container without spawning two to four hearts as usual.
 * If Isaac dies with a, all Red Heart containers will be filled.
 * purges all Red Heart containers and leaves 2 Black Hearts.
 * Mom's Locket refills half a heart each time a key is used.
 * Acquiring an Eternal Heart will allow Isaac to take an extra hit. However, no health will be granted when acquiring a second Eternal Heart or moving to the next floor.
 * The bleeding mechanic from can be tricky to remove, as red heart healing can be rare. Consider skipping this item if you're having trouble healing.
 * spawns double pennies instead of hearts.

Reward

 * The pills unlocked are Re-Lax and ???.