Please give us a game mode to play with hearts
In the old days of Duolingo, people used to play with hearts/lives that you needed to keep alive to complete a unit. Nowadays, the only way to play with these hearts is by making a test that lets you skip units called Testing out, but after you have done that, this game mode is no longer available.
I think it would be nice to have that old playing mode back as a challenge that can be completed for fun or in order to practise. Perhaps make it something that can be unlocked from the Duolingo store like Play with time limit.
By strength bar, I assume you are referring to Health?
When people mention strength bars, they are usually referring to the bars around a Skill. You increase them to get the Skill back to gold. This is a feature on all platforms.
See my other comment for a run-down of the other terms.
I think this is mixing up Hearts and Health.
Hearts is the old game mechanic, from a while ago. It was replaced by the Progress Bar on mobile and the web. You can still see it when testing out (and on Windows Phone I believe).
Health is a new game mechanic they are A/B testing on iOS, that you can bypass with a new currency called Gems. It's a bit confusing that the Health indicator features a heart emblem, but I'm not sure what else they could use.
I believe the OP wants the old game mechanic (Hearts) available as a sort of challenge mode. Given that the code is still there (and used when testing out) it wouldn't be that big a change. It could even be a betting option - two Lingots to play and receive as many Lingots as you have Hearts at the end. Although, some may complain this is encouraging gambling.
Indeed I would like the old game mechanic back as a sort of challenge mode. Maybe something that becomes available when you have completed a skill or when you have trained a skill enough to make it golden.
Since this mode is more challenging than normal mode, it can give you slightly more lingots than a normal game. I don't really like betting, so I think losing the game should display something nice like "Better luck next time". Giving you more lingots depending on how well you score is fine. It can even give you a bronze, silver or golden medal depending on how many hearts you have at the end.
Well, it would be brought back in a different form. In the old days, it was used as a learning mechanism. In the new Duolingo, it can and should be brought back as a reinforcement mechanism.
This is a very practical idea. There is very little programming involved by the Duolingo developers to bring it back, because the code is already there and the feature still exists in a limited form.