Two apps that take a half-formed thought and give it somewhere to go.

Cresendo is where Rheusk and Causaa are built. One turns the idea you cannot quite describe into a script you can film. The other takes what actually happened today and files it under what you believe and what you are aiming at.

They are different apps for different days. They are the same bet: that the useful software is the kind that holds one thought steady long enough for it to become something.

The through-line

  RHEUSK                                CAUSAA

  a vague thought                      something that happened today
         │                                           │
         ▼                                           ▼
      concept                                  ┌─────┴─────┐
        └▸ outline                          belief       goal
             └▸ draft                      the past   what's next
                  └▸ script                    └─────┬─────┘
                       │                             │
                       ▼                             ▼
            a script you can shoot        why it keeps happening

Neither app tries to hand you a finished thing on the first press. Both of them move one rung at a time, keep every earlier version, and let you go back — because a concept turned straight into a script is a script nobody thought about, and a feeling turned straight into a conclusion is a conclusion nobody checked.

The apps

Rheusk

In development

For creators who ship short-form video. It does one thing: it helps you find ideas worth making and sharpen them until they are shooting-ready scripts.

One ladder. Concept, outline, draft, script — and every stage is kept forever, so the version you liked is never gone.
Status is a lens, not a folder. See everything you have sitting at draft, across every theme at once.
It writes in your voice. Suggestions arrive as proposals you accept, regenerate, or edit — and it learns most from the ones you rewrite yourself.
It stops at the script. Not an editor, not a scheduler, not a video generator. The script is the hard part.

rheusk.com →

Causaa

In development

A notebook for the mind. A life is easier to understand when its moments are filed twice — once under what you believe from the past, once under what you plan for the future.

Two trees. Beliefs grow down into why you react the way you do; goals grow up toward where you are trying to get.
One moment, both trees. What happened, what you thought, what you felt — a single note that lives under a belief and a goal at once.
Sentia does the filing. A chat companion that captures the moment in your own words and only reorganises anything after you agree to it.
Paper, not dashboard. Every belief and goal is a slightly-askew page you can pick up and move. No wall of numbers.

causaa.com →

Built the same way

Two products, one machine, no shared data.

Both apps are Flutter on iOS, Android and web, over a Python API with Postgres behind it. They run on the same server and share exactly three things: the front door that terminates TLS, the agent that watches the containers, and the bill.

Everything else is separate on purpose — separate databases, separate backups, separate keys, separate deploy accounts that cannot reach each other. Sharing a machine is a cost decision. Sharing a database would have been a design decision, and not a good one.

Client Flutter — iOS, Android, web from one codebase
API FastAPI, Celery for the slow work
Data Postgres with pgvector; sensitive fields encrypted at rest
Hosting One Hetzner box in Germany, Caddy at the edge
Privacy Each product holds its own data and its own keys

Not a platform, not a suite.

Cresendo is a name for the two apps, not a layer on top of them. There is no Cresendo account, nothing to sign up for here, and Rheusk and Causaa do not read each other's data — or know the other exists. If one of them is useful to you, use that one.

Cresendo is a name, not a company. Rheusk and Causaa are built by Do Duc Anh.