Simple simulators are available (like suggested in the other answer), there are also versions you can run on your own computer instead of the web. But all of these are based on theoretical (idealized) components, meaning a lot of real world parameters are omitted.
The moment you wrote in your question: (based on components specs) (!!), you nearly kept only one option open: PSpice, but it doesn't have a low learning curve at all, but it give the most reliable results a simulator can give (mainly because components are described with real world parameters). These real world parameters mean that a simple resistor is made of a great number of parameters that all need to be fed into the simulator, a simple transistor is even more complex, hundreds of parameters. (many components vendors provide spice components for the components they sell)
The input is a netlist and most EDA systems can create such netlists, but I think for simple tasks it might be overkill.
So maybe just take a look at PSpice and after that, take in account that nearly every other simulator you use, is a theoretical reflection of what is going on in reality and the results might be close to reality but not the reality itself.