Cubicdissection.com - Portal is Dee Dixon's newest Sequential Discovery Puzzle Box. Dee's earlier works like Where's my Hammer and Space Case have been very well received by the puzzle community. Portal carries
Puzzling in wonderlands: The 10 best sequencial discovery puzzles
The First Box sequential discovery puzzle by Wil Strijbos – New2Play
Brian Young Sequential Discovery | Abraham's Well | Mr Puzzle