A digital logic designer and circuit simulator
github.com
github.com
There is also Logisim-Evolution, which also supports VHDL/Verilog and FPGA export.
BUT, I've been using Logisim-Evolution, and it is very nice. An expansion of Logisim that, among other things, does VHDL/Verilog and supports a lot of FPGA boards.
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o Good performance: The example processor can be clocked at 120 kHz.
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o A circuit can be exported to VHDL or Verilog. There is also direct support for the BASYS3 Board and the TinyFPGA BX board. See the documentation for details. The examples folder contains a variant of the example CPU, which runs on a BASYS3 board."
PDS: Looks really nice!
Digital, as the name implies, doesn't deal with the analogue at all, it's a graphical logic simulator. Step-based, fixed signal values like 1, 0, not connected, high-impedance. Think visual Verilog, except somewhat limited.
There is some support in Digital for defining component behaviour in Verilog or VHDL. Once defined, you will get a graphic symbol you can put in your diagram, and all the wires will behave as specified in the code. It's also possible to translate a schematic in the software to Verilog or VHDL code.
Because of that, I do think it would be a good stepping stone to learning more about logic and hardware description languages. I've recommended it before to people who want to learn the basics. But it's still new, has some limits, and I don't think it would scale well to a large project.
Define your circuit with VHDL/Verilog, create a testbench, run the scripts and export to VCD, and then look at the waveforms with GTKwave [1] or your waveform viewer of choice.
write input config files (here: in VHDL) for the simulator (ghdl), and then view the output after x clock ticks (with gtkwave).