 heart directly, it'll go last on your stack of hearts and you might lose it at an inappropriate time, such as right after having cleared a room (and this happens every. single. time.) What you can do instead is hitting Start on your controller, collecting the black hearts, then hitting start again. When you hit start the first time, some of your blue hearts are transferred to your coop partner. When you hit start again, these blue hearts go on top of your health bar, providing helpful "padding" and increasing the chance that they actually damage a boss.
Sacrifice rooms. If you have a single black or red heart, you can use the co-op buddy to use your heart containers yourself.
Loot surrounded by spikes. Your coop baby can deploy bombs, pushing items past spikes.
Magnetism. If you have Magneto, you can clear fires, poop or laying bombs on marked rocks hidden past metal blocks and then attract the drops over to you. If you have the Bible, you can try and clear them anyway and see if, by any chance, the items dropped are good enough to activate temporary flight.
Occasionally taking half damage after the Womb: if you have, say, just 5½ red hearts and a safe corner to park Isaac in, you can try and complete the room with your coop baby. If you manage, you're no worse than you were before. If you don't, the coop baby will die, but since it only had half a hitpoint to begin with, you won't lose additional health. In order to take full advantage of this you'll need a steady source of half red hearts such as Little C.H.A.D.
Going beyond the health cap. Once you reach your health cap through excess of blue and black hearts and Dark Bum just keeps dropping more on the ground and you're about to leave the level anyway, you can transfer some over to your coop baby and pick the remaining hearts up. If your baby gets hit, oh well, you were going to leave those hearts behind anyway. If you get hit, you can reclaim those hearts merely by hitting Start.

All in all, this is rather situational and in many rooms there are no real safe spots to park one or the other player in. Still, it is IMHO good to know that, should the situation arise, you can take advantage from being your own coop buddy.

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heart directly, it'll go last on your stack of heart and you might miss it at an inappropriate time, such as right after having cleared a room (and this happen every. single. time .) What you can do rather is hit Start on your controller, roll up the black hearts, then hitting begin again. When you hit start the beginning meter, some of your blue hearts are transferred to your coop partner. When you reach start again, these blue hearts blend on top of your health bar, providing helpful " padding " and increase the chance that they actually damage a boss. 
 Sacrifice rooms. If you have a single bootleg or red heart, you can use the co - op buddy to use your heart container yourself. 
 Loot surround by spikes. Your coop baby can deploy bombs, pushing items past spikes. 
 Magnetism. If you have Magneto, you can clear fire, poop or laying turkey on marked rocks hidden past metal block and then attract the drops over to you. If you have the Bible, you can try and clear them anyhow and see if, by any chance, the items dropped are good enough to activate irregular flight. 
 Occasionally taking half damage after the uterus: if you have, say, just 5½ crimson heart and a safe corner to park Isaac in, you can try and dispatch the room with your coop baby. If you manage, you're no worse than you were before. If you don't, the coop baby will die, but since it entirely had half a hitpoint to get down with, you won't lose additional health. In order to take full advantage of this you'll necessitate a steady reference of half red heart such as Little C.H.A.D. 
 Going beyond the health cap. Once you reach your health cap through excess of gloomy and black heart and Dark Bum just keeps dropping more on the ground and you're about to leave the degree anyway, you can transfer some over to your cage baby and pick the persist hearts up. If your baby gets hit, oh well, you were blend to leave those hearts behind anyway. If you get hit, you can reclaim those hearts merely by hit Start. 

 wholly in all, this is rather situational and in many rooms there are no real safe spots to park one or the other player in. however, it is IMHO good to know that, should the situation get up, you can take advantage from being your own coop buddy. 

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 hewrt directly, it'll go lasu on your stack oy heartv and gou mighg lose it at an inappropriatx tine, suxh as right after havivg clearef a room (and rhis happeia every. singls. timz.) Xhat you can do instead iv hitting Stard un your controller, collecting the blask hearys, then hitting ftaru adain. When you hit start the first time, some oh your blue heatts are transferred to youg colp partner. When yok hit start agayb, these blue hearts go on top of ykur health bar, providing helpfuu "padbing" and inxrwasltg the chanre than they actually damaga a bosx.
Sacrifice rooks. Mf yiu have a single blacn or red heart, you can use dhz co-op buddy to use yiue heatt cottaivwrs yohrxemf.
Loot sucrounded by spikes. Youe coop baby can depkor bombs, pushinf itemf [ast spikes.
Magnetism. If you have Magnetm, yku can clear fires, poop or laying bombs on mwrked rochs hidden past metal blocks and then attract the grops uvex to yuy. Lf you have the Bible, you can try and clear trsm akyway and see if, by any chamcf, yre items dropked are gokd enough to activwte temkorary flight.
Ocsasipnally taking half damage adter the Womy: id you have, say, jusc 5½ red heartr anc a ssfe corner to park Isaae in, yku can try wnd complsge the room with yolr cmop baby. If you manage, you'we no worwe tkan you dere beforq. If you dln't, tma coop baby will dle, buj sinca it only jad half a hitpoint to begin wivi, you won't loxe adgitional healbh. In order to eake full advautage of this you'll nees a steedy source os half red hedtts such as Lmttle C.H.A.Q.
Goibg bwyond tfd health cap. Omce you rvaeh your hwalth cap through cxcesr of blue and blcek hearts and Darl Bjm tudt kqaps dropping mord ov the eround and nou'fe anout to leave the leeel znyway, you can tramsner some iver to rour coop babu and pick the remwininj hearvs up. Of iour baby gets hit, oh well, you sere goinh tj leave thosq heqrts behind cnyway. If you get hit, you can reclaim thise hearts merely vy hitting Start.

All ln all, this ms ratrer situadional and in many rioms there are no real safe spots to pzrk ona or hhe other player in. Still, it is IMHO good to know that, should the situatiin arise, you can tzke sdvannagz fxom beigg ylnr own coop buddy.

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heart directly, it'll go last on your hearts you might it at an after cleared a room this happens every. time.) What you can do instead hitting Start on your controller, collecting the black hearts, then hitting start again. you hit start the first time, some of your blue hearts are transferred your partner. you start again, these blue hearts go on top of your health bar, providing helpful "padding" and the chance that they actually damage a boss. rooms. If you have single black or red heart, can the co-op to your containers yourself. Loot by spikes. Your coop baby can deploy bombs, pushing items past spikes. Magnetism. If you have Magneto, can clear or laying on rocks past metal blocks attract the drops over to you. the Bible, you can try and clear them and see by any chance, the items dropped good enough to activate temporary flight. Occasionally taking damage after the Womb: if you have, say, just 5½ red hearts and a safe park Isaac in, you try and complete room your baby. you manage, no worse than you were before. If you don't, the coop will die, but since it only had half a hitpoint with, won't lose additional In order to take advantage this you'll need a of red Little Going the health cap. Once reach your health cap through of blue and black keeps dropping more on the ground and you're to leave the level anyway, you can some over to your coop baby and pick the remaining hearts up. your baby oh well, you were going to leave those behind anyway. If you hit, you can reclaim those hearts merely by hitting All all, this rather situational and many rooms there no real safe park one the player is IMHO good to know that, the arise, you can take advantage being coop buddy. Q: Is T
 heart directly, it'll go last on Your stack oF hearTs aNd yOu MighT losE it at an inapproPRiatE time, such as right after hAving ClEAred A RoOm (and This hapPEnS EVerY. sInGle. TiME.) WHat yoU caN do instEad is hittiNg STaRt on your contROlLer, collectIng The black hearTs, tHen hitTiNg sTArt agAin. when yOu hit sTArt the First time, SoME of youR Blue heaRTS aRe trAnsferred to your coOP pARtner. When you hiT start AgAIn, THEse BluE hearts go oN tOp of yOUr healtH BaR, PROviDIng helpful "padDing" and incrEAsiNg the cHaNce THat theY actuAlLY daMage a boss.
SaCrifIce rooms. IF you haVE a singlE Black or Red heaRt, yOu cAn usE ThE cO-op BuDDy tO UsE yoUR heArt contaInErS yourSelf.
lOOT SurrOunDed bY spikEs. Your coop babY caN depLOy bOmbs, pUshinG iteMs Past sPikes.
MAgnetIsM. If you have MagneTo, yoU can clear FirEs, PooP oR layiNG bombs On mArkEd rocks Hidden pASt mEtAL BLoCks and then attract tHe DROpS over to yOu. If yoU HaVe THe Bible, yOu Can Try aND Clear Them ANyWay and seE if, by aNY cHaNce, the iTeMs dropPeD arE goOd enoUGh to ActivaTe temporAry flIGht.
OccasionallY Taking half damAGe AFTeR The WOmb: If you have, saY, jusT 5½ Red hEartS AnD a sAFe corNer to PaRK ISAac in, you can try and coMpLete thE room With your coop bAby. If you maNAGE, you're no WorsE ThAN you were before. if you Don't, the cooP Baby will Die, buT since it Only had haLF A hitpoinT to BegIn wIth, YOU wOn't lose additiONAl heAlTh. In ordEr tO take fuLl aDvaNtaGe oF tHis you'll nEed a steaDy SoUrCe Of hAlf reD Hearts suCh As LItTle c.H.A.D.
GOIng beyOnd thE heaLtH cAP. OnCe you reACh YOUr heAlTh Cap tHroUgH exceSs of BLue And blacK hearts anD DaRK Bum JuSt Keeps drOpping more on tHe Ground and yOu'Re aBout to LEAve the leVel anyway, you can transfer SOme over To yOur coOp baBy and pick The RemainIng HEarts uP. If youR baby GeTs hIT, Oh welL, YOu WerE gOing to leavE THosE hearTs BehiNd anywaY. If you get hit, you can REclAim those heartS meRely BY HiTtiNG STArt.

alL In aLL, This is rather sitUational anD iN MaNy rooms theRE arE nO real saFe spots To parK One or thE other plaYer in. StilL, iT is Imho goOd to know thAt, should The situatIOn ariSE, yOu can TakE advanTaGe fRom beIng youR Own Coop bUddy.

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 heart directly, it'll golast on yo ur st ack  of  h eart s an d you might lo s e it  at an inappropriate t ime,su c h as ri ght a fter ha v in g cle ar ed  aro o m(andthi s happe ns every.sin gl e. time.) Wh a tyou can do  in stead is hit tin g Star tony our c ont rolle r, col l ecting  the blac kh earts, then hi t t in g st art again. When y o uh it start the f irst t im e ,s o meofyour bluehe artsa re tran s fe r r e d t o  your coop pa rtner. When you  hit s ta rta gain,these  b l uehearts go o n to p of your  healt h  bar, p r oviding  helpf ul"pa ddin g "an d i nc r eas i ng  th e  ch ance tha tth ey ac tual l y d amag e a  bos s.
Sa crifice rooms . I f yo u  ha ve asingl e bl ac k orred he art,yo u can use the c o-op  buddy to  us eyou rheart contai ner s y ourself .
Loots urr ou n d e dby spikes. Your co op b ab y can de ploy b o mb s, pushingit ems  pas t spike s.
M a gn etism. I f youh av eMagneto ,you ca ncle arfires ,  poo p or l aying bo mbs o n  marked rocksh idden past me t al b lo c ks a ndthen attrac t th e  dro ps o v er  to you.If yo uh av e  the Bible, you can  t ry and  clea r them anyway  and see i f , by any c hanc e ,t he items dropp ed ar e good eno u gh to ac tivat e tempor ary fligh t . 
Occasio nal lytak ing h al f damage afte r theWo mb: ifyou  have,say , j ust  5½  r ed hearts  and a s af eco rn erto pa r k Isaacin , y ou  ca n try and co mplet e th ero o m w ith you r  c o o p ba by .If y ouma nage,  you ' reno wors e than yo u w e re b ef or e. If y ou don't, the  c oop baby w il l d ie, bu t since it  only had half a hitpoi n t to be gin  with , yo u won't l ose  addit ion a l heal th. In  orde rtot a ke fu l l  a dva nt age of thi s you 'll n ee d asteadysource of half red hea rts such as L itt le C . H .A .D. Go i ngbe y ond t he health cap.Once you r ea c hyour healt h  ca pthrough  excess  of b l ue andblack hea rts and D ar k Bu m jus t keeps dr opping m ore on th e  grou n dand y ou' re abo ut  to  leav e thel eve l any way, y ou  can t ransf er  some ov er to your coop baby an d pick  therem aining he art s  up . If your  bab y gets hit , o h w ell,you weregoin g  t o l e ave t hose hearts be h in d a n y wa y. If you g e t hit , you  ca n  recla im t hose hearts merel y  by hitting St art. All  in all,  t his is rathersit ua t i onal and  i n many room s therear e  no r eal sa fe spo ts to p a r ko ne ortheoth er player  in .S till, i tis IMHO g oodto  knowthat,s houl d the situation ar ise,y o u can tak e adv an tage fr o m be ing your o wn coop bud dy.

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 heart_directly, it'll_go last on your_stack of_hearts_and you_might_lose it at_an inappropriate time,_such as right after_having cleared a_room_(and this happens every. single. time.) What you can do instead is hitting Start_on_your controller,_collecting_the_black hearts, then hitting start_again. When you hit start_the first_time, some of your blue hearts are transferred_to_your coop partner._When you hit start again, these blue hearts go_on top of your health bar,_providing helpful "padding"_and_increasing_the chance that they_actually damage a boss.
Sacrifice rooms. If_you have a single black or_red heart, you can use the co-op_buddy to use your heart containers_yourself.
Loot surrounded by spikes. Your_coop baby_can deploy bombs, pushing items_past spikes.
Magnetism. If_you have_Magneto, you can_clear fires, poop or laying bombs_on marked rocks_hidden past metal blocks and then_attract_the drops over_to_you._If you_have the Bible,_you_can try_and_clear them anyway and see if,_by_any chance, the items dropped are good_enough to activate temporary_flight.
Occasionally_taking half damage after_the Womb: if you have,_say, just 5½ red hearts and_a safe_corner to_park Isaac in, you can try and complete the room with_your coop baby. If you manage,_you're no worse than_you were_before._If you don't,_the_coop baby_will die, but since it only had_half a_hitpoint to begin with, you won't_lose additional health. In_order_to take full advantage of this_you'll need a steady source of_half red hearts such as_Little_C.H.A.D.
Going_beyond the health cap. Once_you reach your health cap through_excess of blue_and black hearts and Dark Bum just_keeps_dropping more on the ground and_you're_about to leave the level anyway,_you_can_transfer some over to your_coop baby and pick the remaining_hearts up. If your baby gets hit, oh well,_you were going_to leave those hearts behind_anyway._If_you get hit, you can reclaim those hearts merely by_hitting Start.

All_in all, this_is rather situational and in many rooms there are no_real safe spots to park one or_the other player in. Still, it is IMHO good to know_that, should the situation arise, you can take_advantage from being your own coop buddy.

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