I have had the trial for this on my phone for ages and just recently started to play with it. So far I really like it so much so that I thought I would tell you a bit about it.
there are versions for android, ios and even a version thats supposed to run on chrome (wont work for me however) you have a work board which allows you to put various compnents and "wire" them up, the components are configurable to match transistors, resistors etc you may have to hand.
It falls short on ic's however with just the options of 555's, counter chip and a 7 segment led driver but for 6 quid for the ad free larger workspace version you cant expect too much.
It allows you to run oscilloscope traces on any part of the circuit you make and slow down or speed up the simulation.
I did a practice circuit on it yesterday which I then copied onto a breadboard at home and was getting very similar results to the predicted results.
The one main snag I found so far is the way it deals with AC voltages seems all wrong to me but that could be me not getting the settings right.