Brand spanking new to Houdini, and 10 mins in already stuck :?
Ive added some geometry and now I am unable to tumble, pan, or dolly my viewer. And instead I get a marque selection. Whats up? What did I do?

You're probably in select mode. Either press Esc to return to View mode, or hold down Space to temporarily tumble. If those don't work, then I'm not sure what you've done :?

Esc.
lol
Thank you

scscop
Esc.
lol
Thank you

Houdini interface = heaps of perplexities but worth it.