Kinetica

Kinetica is a two-handed keyboard. Both thumbs swipe or tap at the same time,
independently, and the two gesture streams merge into one word.

Typing "something": the left thumb taps S, then E, while the right thumb
swipes O -> M and then T -> H -> I -> N -> G. The streams are merged by
timestamp into S + OM + E + THING.

It is a spiritual successor to the discontinued Nintype, written from scratch
on Android's public IME APIs - not a fork, and with no third-party gesture or
prediction library. The dynamic time warping, the trie search, the path
resampling and the dual-stream merge are all in the app, so every constant is
understood and tunable.

The manifest declares no INTERNET permission. Nothing you type can leave the
device, because there is no code path that could send it. Decoding, prediction
and learning are local, the personal dictionary is on-device storage only, and
password or private fields switch off suggestions, trails and learning.

Features

* Two independent swipe/tap streams merged by timestamp, including
near-simultaneous order swaps and mid-swipe cross-thumb taps for double
letters
* Swipe decoding written from scratch: banded dynamic time warping over
arc-length-resampled paths, an anchored trie search, frequency and
bigram-context scoring
* English, Italian, Spanish and Polish: 46k to 49k words and 62k to 100k
bigrams per language, with real corpus frequencies. Accented words are
matched through their base-key path and restored on commit (pozno -> późno)
* Tap autocorrect with three aggressiveness levels
* Live completions while you tap, and the letters you actually typed are
always a pickable suggestion, so a word the dictionary does not know still
commits verbatim
* Personal weighting, kept per language: words you commit rank higher over
time, long-press a suggestion to reinforce it, slide up or down while
holding to change by how much
* Long-press alternates on every key, customizable edge swipes, chord
shortcuts, a two-page symbols layer and a numpad
* Five layout modes (full, right, left, split, one-handed), adjustable
height, a dark theme, Material You wallpaper colors, or a whole palette
derived from one custom color
* Peck-type mode that switches decoding off entirely, for slang and anything
else the engine would otherwise mangle
* Reversible backspace slide: the span to be deleted is previewed
struck-through, sliding back retracts it, and only lifting commits it
* Dictionary management on the device: import an AOSP wordlist.combined,
export or import your personal dictionary as JSON, reset it per language

Source, build instructions and the full feature list:
https://github.com/EZ-eta/kinetica

If Kinetica is useful to you: https://ko-fi.com/ez_eta

Automatic spaces after tapped words, off by default. Words with apostrophes
(don't, dell'anno) and single letters (a, I) get one too, and a space you
delete no longer comes back. Three timing sliders.
The top-row up-swipe types its digit again.
A forward slash on the symbols page.
The spacebar's cursor slide has an adjustable speed and can move by word.
An optional retype button on the suggestion bar.
Lower input latency, contributed by pigmej.
Macron o, contributed by lucylouwebart.