CAUSTIC

Questions, bugs, or a level you are convinced is impossible — write any time:

deanconnorl@icloud.com

You will hear back within a few days.

Drag one finger anywhere on the screen. That lays down fluid, and light bends toward whatever is thicker — the way a heat haze bends the road behind it.

So the side you draw on decides which way the beam goes. To pull light down, stroke below it. To lift it up, stroke above it. Getting that backwards is the single most common reason a level will not come out.

The ring is a colour and nothing happens when I hit it.

A ring drawn in one colour accepts only that wavelength. Pointing the whole beam at it does nothing, however bright it looks.

Each colour bends by a different amount, so the beam has to be turned hard enough to pull the spectrum apart, and then the right band landed on its own. Violet bends hardest and swings furthest. Red bends least and stays nearest the straight path — so a red ring usually needs a gentler touch, not a stronger one, which is the opposite of what it feels like.

My light has gone dim, or disappeared.

Fluid is glass, and light loses a little of itself crossing it. A few deliberate strokes are a lens. A screen covered in fluid is fog, and the beam can fade out entirely before it reaches anything — even while the bar at the bottom says you have plenty left to spend.

If that happens, reopen the level from the counter at the top right. It starts clean.

The ring keeps moving, or my glass keeps fading.

That is the sixth chapter, Tide, working as intended. Some rings drift back and forth, so the beam has to follow them rather than be aimed once. On some levels the fluid fades on its own, so a lens has to be kept fed while you hold the light on the ring.

Watch a moving ring make one full trip before you touch the screen. It travels in a straight line at a steady pace, so you can time it.

Why are some level numbers gold, silver or bronze?

That is how you solved them. Finish a level in a single stroke and it turns gold; two strokes is silver; more is bronze. Only your best counts, so replaying a level can never take a medal away.

I have run out of fluid.

The bar along the bottom is your budget, and it is measured in how far your finger has travelled — not in strokes and not in seconds. Short, placed strokes go a very long way. Most levels are meant to fall to one or two.

Reopen the level from the counter at the top right to start it over with a full budget.

I am stuck and I want to move on.

Tap the counter at the top right — the "12 / 49" — to open the level select. You can go back to anything you have finished, and you can move past a level that has beaten you. Nothing is locked away for good.

There is no sound.

Caustic mixes politely with whatever else you are playing, which means it also respects the silent switch. If your phone is on silent, the app is silent. Flip the switch, or raise the volume while the app is open.

The sound is one tone that swells as a ring fills, so it is quiet by design until light is actually landing on a target.

Does it work on iPad?

Yes. The playfield is a fixed shape on every device, letterboxed into whatever screen it is given, so a level is exactly the same puzzle on an iPad as on a phone. Your progress is kept per device.

Is there anything to buy, or to sign up for?

No. One purchase, forty-nine levels. No advertising, no in-app purchases, no account, no network connection, and nothing collected about you. See the privacy policy.