Diffhall Hall Pass $1.95/moFree during preview
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Lobby Rooms Notebook Review Card Pricing

Rooms

01Ask for work you can check 02Read the whole diff 03Keep secrets out of the code 04Treat every input as hostile 05Check who is asking 06Check that it exists 07Make tests able to fail 08Plan for when it breaks

Hall Pass $1.95/month or $19.50/year · one room $1.00 · Free during preview

Pricing

Free to walk in. $1.95 a month for the whole hall.

Every reading is free. Start on the free benches; take the Hall Pass when you want them all, your notebook on every device and the Review Card.

Walk-in

Free

  • Every room's reading and sources
  • Rooms 1 and 2 in full (4 benches)
  • The first bench of every other room

Hall Pass

$1.95/month

or $19.50 a year (two months free)

  • All 16 benches, as often as you like
  • Your notebook: every read kept, on any device, by private link
  • The printable Review Card

Free during preview

One room

$1.00

paid once, kept

  • Both benches of the room you choose
  • Your reads of it kept in your notebook

Free during preview

Preview: payments are not switched on yet, so every room and bench is open to everyone and nothing is charged. The prices above are the prices that will apply when checkout opens; nothing renews or charges without you choosing it then.

Questions

What do I get for $1.95 a month?
All sixteen benches (the six that are not free, plus the free ten), as many tries as you like, your notebook kept and opened on any device by private link, and the printable Review Card.
Is there a certificate at the end?
No. Diffhall is a self-study website, not a school or college. It awards no certificate, credit, grade or qualification of any kind, paid or free.
How do I pay?
You do not, yet. Checkout is not switched on during the preview, so everything is open and free. When it opens, payment will be through PayPal; the Hall Pass will renew until you cancel, and cancelling stops the next payment.
What does "one room" mean?
Both benches of one room for $1.00, paid once and kept. Rooms 1 and 2 are already free.
Is there AI on the site?
No. Every reading, bench and note was written for this site and checked against the linked sources; no AI runs on the site and nothing you tick is sent to one.