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.
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.