This is quite frustrating and confusing in the multiple choice question, where both were offered, but I wasn't sure whether I should pick one or the other or both. I lost a heart for picking only the one without a space. In standard Irish orthography, only the version without the space is considered correct, right? Anyway, if possible, I don't think both should be offered at the same time during a multiple choice question.
It was the old system on Duolingo, where you would start each lesson or practice with three hearts, and would lose a heart for each incorrect answer (there were other short-lived variations of this as well), and would fail after a fourth incorrect answer, thereby having to restart the lesson. I must have written that just before they phased it out, because it's been gone for quite a while.
Windows 10 users can experience the "Hearts" scoring system by installing the Duolingo App from the Microsoft App Store - it still uses the hearts scoring system.
(It also uses the system spell checker, so if you have the Irish GLE keyboard layout installed and selected when you run the app, it will correct some of your spelling mistakes in Irish!)