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.
Where everything sits
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 §06.
03 The ring is the button
Every one of the game’s interact points — a station keeper, a passage mouth, a cover, a salvage haul, a Pearl shell, a creature your net could actually hold — draws its own marker in the water the moment you’re close enough. On a keyboard that marker is the familiar keycap with a letter on its face. A phone has no key to draw, so on a touch device it’s a plain tap ring instead: a filled disc with a bright rim, floating just off the thing itself.
Tap that ring and it doesn’t just point at a button somewhere else — it fires the action directly, right there: talk, step through, crack the cover open, haul the wreck in, prise the shell, throw the net. It runs through the exact same handler the T or C key fires on a keyboard, so a tap on the ring can never do something different from what the key would. The labelled button down in the action row (Fig. 2, below) still sits in its usual corner as a second route to the same action — reach for whichever one your thumb is already nearer to; neither is required over the other.
One honest gap: a Pearl shell draws its own ring exactly like everything else above, but hasn’t earned a labelled corner button of its own yet — reach it by tapping the ring directly. See Pearl Shells for what prising one actually pays.
Two rings that look similar and mean different things
A creature or a crystal worth taking glows with its own soft halo the instant you’re in range — colour-matched to a creature’s own rarity, a plain warm glow on a crystal or a shell. That halo is a STATE, not a button: it means “this is worth having,” nothing more, and tapping it alone does nothing. The tap ring — filled, hard-edged, pulsing, described above — is the CONTROL, and it’s the only one of the two that answers a tap. The two can share the same creature at once: the halo is the promise, the ring is how you cash it in. A net-throw ring specifically is only ever drawn once a net you actually own can hold whatever’s in front of you — never earlier — so the screen never invites a tap the throw is about to refuse.
The ring itself is drawn small on purpose — legible, not obtrusive — but what answers your thumb is a generously oversized tap target centred on it, well past the ring’s own drawn edge, so a press anywhere close still lands cleanly.
Miss on purpose or by accident — tap a cover that’s still locked, or a haul too heavy for the arm you’re carrying — and the game says why rather than staying quiet about it. The first time that happens, a small card explains it plainly on the spot; every time after, the same short line you’d already see on a keyboard does the job on its own.
04 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.
Desktop key → touch equivalent
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.
05 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.
06 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 desktop the same button sits in the same corner and also takes a key — H, drawn right on the button, rebindable in Setup like everything else in Getting Started.
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.