I highly recommend the Outlier Dictionary, an addon for Pleco. It covers about 4000 characters, so won’t include very rare ones like 忻. Pleco itself will show basic decompositions like 忻 = 忄+ 斤.

There used to be an offline mobile app for HanziCraft, but the app seems to be gone now (a little annoying, since I’m pretty sure I paid for it).

Project Euler if you don’t mind more mathematical problems.

If you happen to speak Chinese, PTT.

Redirector?

An air horn.

[email protected] would appreciate this post (and you might like the whole instance if you’re not already aware of it).

[email protected]

For anyone on Lemmy interested in these issues there’s also a [email protected].