← The Pilot’s ManualChapter 14

Playing on Mobile

Bathysia is fully piloted on a phone — a docked joystick, a contextual action row, a console row for your abilities, and a HUD that gets out of your way in one tap. Nothing here is a cut-down mode; it’s the same drone, the same water, the same keys, just drawn for a thumb instead of a keyboard.

01 The layout

The touch layer only appears on a touch-primary device — a mouse-and-keyboard session never sees any of it, pixel for pixel. Every piece below reads its position off one shared coordinate system (a phone’s safe area, banded top to bottom), so nothing on this list can drift into another without the whole stack being rebuilt with it.

Fig. 1

Where everything sits

JoystickDocked bottom-left — always drawn, drag from anywhere in the left half

Action rowAssign on the left, Interact on the right — only when either is live

Console rowYour class’s ability tiles plus the capture tile, centred above the stick — see Abilities

Console & ChartTwo tiles, upper-right, below the top cards

HUD toggle & fullscreenStacked in the very top-right corner

02 The joystick

The stick is a real object now, not a ghost that only appears once you touch the screen: it sits docked in the bottom-left corner, inside the safe area, drawn at rest for a thumb that hasn’t moved yet. Land on the dock itself and it steers from its own centre, like a physical stick. The old habit still works too — press down anywhere else in the left half of the screen and the ring re-anchors right there under your thumb instead, then snaps back to its dock the instant you let go.

Drag and a knob inside the ring follows your thumb, clamped to the ring’s radius; push it to the edge for full thrust, ease it toward centre to glide. Let go and the knob eases back to rest on its own, no elastic snap.

Only one thumb drives the stick at a time — a second finger landing in the zone is ignored rather than fighting the first for control.
Opening any full-screen panel (the Console, the Chart, a dialogue, first launch) suspends the stick along with the rest of piloting — it reappears the moment you close whatever you opened. The stick and the sonar scope are the two things a “hide the HUD” tap never touches — see §05.

03 Every key, tapped

The rule this manual holds the game to: whatever a keyboard can do, a thumb can too. In practice that means most controls sit right where you’d expect a phone game to put them, plus two screens (the Console and the Chart) that swap a keypress for a tap on their own rail tile.

Fig. 2

Desktop key → touch equivalent

Interact buttonBottom-right of the action row — reads the live verb (“Talk to Bell”, “Enter the passage”, “Open the cover”), only shown while something answers it

Assign bannerBottom-left of the action row, only shown once a charted field is waiting on a drone

Q / W / E

Ability tilesThe same three glassy tiles the ability bar draws on desktop, tap in place of the key — see Abilities

Capture tileTap once to aim, tap again to throw — the prompt literally says “Tap the pod again to throw”

X / Z

Strike / Ring buttonsFull-width buttons inside the Sealed Grotto's own siege screen

I / K / L / P / R / ?

Console tile, then its tabOne rail tile opens the Console; its own tab rail is tap-driven throughout

Chart tile, or the sonar scope itselfTapping the corner scope opens the Chart exactly like clicking it on desktop

The eye-icon buttonTop-right corner — see §05

Showcase buttonInside the Console's Drone tab, not a key of its own on touch

One honest gap: planting a new Survey Beacon (B) has no tap button yet — it is keyboard-only today. A touch pilot can still travel to any beacon already planted, straight from the Chart.

04 Fullscreen, and Add to Home Screen

A small square button sits top-right, just under the eye-icon HUD toggle, on any device that genuinely supports it — tap it and the browser’s own address bar and chrome drop away. The choice is remembered — if you leave fullscreen and dive back in later, Bathysia re-arms it on your very next tap or key press rather than fighting you for it every single session, since a browser will only grant fullscreen off a real gesture, never on load.

Honestly: iPhone Safari has no true fullscreen for a web page at all — a browser limit Bathysia can’t route around, not a bug here. On that device specifically, Add to Home Screen is the real answer — launch the game from that icon instead of a browser tab and it opens with no browser chrome whatsoever, which gets you the same chrome-free window fullscreen would have. Where the game detects this genuine limitation it says so once, in a small dismissible note, rather than showing a button that would silently do nothing.

05 Hiding the HUD

One icon button, always visible in the top-right corner — a bare eye, no label, sized well past the 44 px touch floor. Tap it and every piece of chrome sweeps away at once: the resource readout, the depth & collection card, the Console/Chart rail, the objective chip, the ability bar, the action row. Tap it again and all of it comes back. On a keyboard the same tap is bound to H.

Two things deliberately never leave, hidden or not: the docked joystick, because a “clean screen” that strands you mid-swim isn’t a feature, and the sonar scope, because tapping it is how you reach the Chart — which is how you reach the Berth, every other region and every beacon. The button itself turns amber while the interface is hidden, so “the chrome is off” is a state you can see at a glance, not something you have to remember you did.

This replaces an earlier version of this same feature — a row of small, unlabelled per-group handles down the left edge. They tested badly (nobody found them) and are gone from the game entirely; one visible button that does the whole job replaced them. If you remember four little squares from an older build, that build is out of date, not this page.

The full keyboard binding list, corrected for this pass, lives in Getting Started.