LACUNA

1. Tap the button above, then Open when the download finishes.
2. Android will say the file can't be installed from this source — tap Settings and allow Install unknown apps for your browser.
3. Go back and tap Install. Play Store Protect may warn about an unknown developer — that's expected for a test build.
4. Open LACUNA. Tap to advance, tap choices, use MENU → SAVE before big scenes.

Test build — no analytics, no network calls, saves stay on the device. If it crashes, send me the phone model and what you tapped.