Cheaper to emulate something new than risk burning up the 555... the downside is that you have to pay for the full version and extra components...
having said that, it's cost me $13 bucks all up has taught me more about electronics and understanding than hundreds of dollars spent on courses over the years due to the way it's visualized...
Looks like yet another port of Falstad's Circuit Simulator. I still use that as my primary sim. It's no SPICE, but in terms of sketching out an idea and getting a rough guess at the viability of a circuit, it really cannot be beat. Every electronics hobbyist should download a copy.