Guppy gives you a fly for every kill (might be for every tear landed, it's been a while) It's lethal if you can bring down enemies quicker than the fly's can get to them.

Went for some high risk devil trading yesterday and ended up with a beast of a build, which was made even better by getting cancer before reaching mom. I ballsed up one room right near the very end though meaning I had no stone hearts to protect me in the last battle. Was a close one but I failed. Boo.

I was annihilating everything in my path almost instantly. I also had the thing where you draw a circle on the floor and it damages whatever is inside. Just didn’t have the health to finish mom off.

Yes Nina! Isaac is the GOAT!

I love the way they themed that challenge, always elicited a small lul when I saw it in the list.

Yeah I think I switched to hard mode quite early but that's because the hooks were in and I was dead set on trying to 100% it.

I'd say switch to it, but if you aren't enjoying it then put it back in normal mode for a while and then go back when you feel like it.

For me, the fun thing about Isaac was that in the end it didn't become a game about trying to complete every run, it just became about seeing what crazy shit would end up happening during a game. For me, Isaac is one of the very few roguelike games where there is enough depth to keep you coming back without it getting repetitive and I think a lot of that is down to the way the game handles weapon and item combos and is quite happy for you to break the game.

I think an example if something that I thought I was gonna love but write quickly fell off was Gungeon, I was so hyped for that game since it has a ludicrous number of guns that work in cool ways, but there's almost nothing in the game that changes how any of the weapons work so after a while it becomes really repetitive, I would make the same complaint about Dead Cells. Both games are really good, but for me both had a shelf life, I dumped over a thousand hours, maybe 1500 into Isaac and although I probably won't go back, none of that time felt like it was a grind or a chore.

I would highly recommend playing Hard only as some unlocks require Hard mode completion. However if you unlock on Hard mode you also unlock whatever Normal mode would've unlocked.

In case you didn't know, there's new DLC coming... https://bindingofisaacrebirth.gamepedia.com/The_Binding_of_Isaac:_Repentance

Would anyone have any tips for that Solar System challenge? I want it done, but I really struggle, usually get 3-4 floors in.

Also, do items like the pentagram do anything with the flies? Or is that a wasted heart on the devil deal?

All of your questions apart from "Is each run a start from complete scratch?" aren't super interesting to answer as they're things to learn as you play. Your runs are all fresh, but items that you unlock through runs are added to the pool, so there is a sort of progress. Everything else - experiment.

Anyone getting this then?  https://studio71games.com/collections/frontpage/products/the-binding-of-isaac-four-souls-game

Someone help him and I might try it again. Poo and snuff and blood and that.

Tempy answered all of the issues like a boss so I'm just gonna chip in a couple of other bits and pieces in response to Muzz. 

acemuzzy wrote:

deals with the devil stuff - I like ended up with no red hearts, and then with a collar or something that insta revived me back outside the room, as in it was impossible to die.  very strange.  is that basically for leet players / high risk vs. reward?  I'm kinda thinking I may stay clear for the moment cos I need all the hearts I can get!

Not for leet players, don't ever think there are things in this game you should be leaving, the experimentation with things and discovery is half the fun in this game. 

acemuzzy wrote:

unlocked a couple of characters, but i guess will stick with isaac for the mo

Issac is a strong character because he starts with the D6 but the other characters all have different characteristics that will give the early parts of the game a bit more variety - in the case of some characters the differences are big enough to change the way you approach the whole run. Again, nothing in this game shouldn't be tried if you see it. I 100% recommend giving them a look especially if you click with one of the characters or prefer them to Isaac while you're getting into things. 

acemuzzy wrote:

was trying rebirth on bone, and vanilla (well, wrath of the lamb) on pc, and yeah they look a little different etc. but mechanically is it worth upgrade?  and what about afterbirth?  Is that basically all stuff I wouldn't be hitting for a while yet anyway?

In addition to Tempy's comments, Afterbirth adds Greed Mode which is a slightly different type of playing the game which is a bit like a boss rush mode. You don't need the DLC for this unless you're enjoying the game and want to see everything it has imo. 

acemuzzy wrote:

stuff that's the other side of a ravine I can't cross... do i need floaty powers or something?

I'd also add here that there is no guarantee that there is anything that will help you cross the ravines in a run, so don't worry if you can't reach something. The only exception to this is if you have a rock next to a single square gap, you can place a bomb next to the rock and it will fill in the adjacent hole. Also look out for rocks that are a slightly different shade to other rocks around them, and look out for any rocks that have a little X mark on them or are glinting occasionally, they're pretty rare, but if you spot one and have a bomb, it's worth blowing them up as they contain hearts/keys/bombs and occasionally chests.

Lol i have it on bone, steam and ps4, and I'm not even sure if I like it or not.  Gonna try to give it some more love than previously though.  Wish it would tell you what the powerups you have do more clearly though - but i guess I'll gradually recognise some.

Thanks all for the answers!  

If you finish a run and it says you've unlocked something, it can then turn up in the loot pool for all subsequent runs, that's it.

Not sure I've had this yet then .  Or maybe I have for like character stuff, but that's kinda different to loot.

What do you mean by loot? Keys, coins, cards, pills, batteries? They are run only. Any pickups that you earn - the game will literally say “You’ve unlocked... Cain’s Eye” (as an example) will mean that Cain’s Eye is shuffled into the pool of pick-ups that can appear. But it’s still random, not guarantees, because it’s a roguelike.

If you want to know what pickup does, use the platinum god site. There are far too many items to memorise all of them unless you’re dedicating hours to it every day, so knowing which syringe you’re about to grab or ignore because it will either make you really strong or kneecap you because of how your stats currently are is something always worth checking if you can’t remember.

Took me a while to even find the "use item" button which didn't help confusion and explains why I wasn't able to pick sine things up. I was more meaning passive things, like a got a leaf and had no idea what it was changing about me.