The studio
HollowNest Interactive is a trading name of Flowroll Ltd, registered in England and Wales and working from Cellan, near Lampeter in west Wales. It is a small studio, and the smallness is the point: whoever designs a thing here builds it, ships it and answers for it.
We are drawn to software that makes a hidden process visible. Most tools hand you a result and keep the reasoning to themselves; ours are built the other way round, so the working is the product and the answer falls out of it.
Everything runs on the device. No accounts stand between a person and the thing they opened the app to do, nothing phones home, and nothing we publish stops working when a server we might once have rented is switched off.
Android development
Native applications written and maintained here — parsers, renderers, animation loops, release engineering and the compliance work Google Play asks of a publisher.
Making process visible
Deciding what to animate and, harder, what to leave still. A diagram states a fact; a sequence you can pause at the wrong step teaches the reason behind it.
Writing the lessons
Explanations composed alongside the software rather than after it, so the words and the behaviour cannot drift apart between releases.
Publishing and care
Store presence, releases, updates and correspondence for everything in the catalogue. The address under Contact reaches a person rather than a queue.
Treecalc
A calculator that shows its working. Give it an expression and instead of returning a number it parses your input into a syntax tree, draws that tree node by node, then evaluates it from the bottom up — so precedence and parentheses stop being rules to memorise and become something you watch happen.
The expression is split into tokens, assembled into a tree that respects precedence and associativity, then walked to produce the answer — each stage laid out rather than assumed.
Watch subexpressions collapse into values one at a time, or take the answer straight away. Whichever you pick is remembered as the default.
The reverse-Polish form is shown too, so infix, tree and stack evaluation sit together instead of in three separate chapters.
A curated library demonstrates single rules — associativity, a unary minus around a power — and each stage of the pipeline carries a short lesson with an expression to try.
A searchable history of every calculation, clear errors pointing at exactly where an expression breaks, and no account, connection or advertising anywhere in it.
Company and contact
- Registered company
- Flowroll Ltd, England and Wales
- Trading as
- HollowNest Interactive
- Director
- Owain John Harvey
- Registered office
- Glanteifi, Cellan
Lampeter SA48 8HU
United Kingdom