ACID RAIN

About the game

In ACID RAIN you are a small miner with a drill and a bad forecast. Each day is a single screen of earth with a strip of sky on top: you start at the surface, and the exit door is somewhere at the very bottom. Rain falls from above, pushed sideways by the wind, and every drop that hits you costs a heart. The ground above you is your only shelter, but the rain is acidic and slowly dissolves the earth it lands on, so the longer you take, the thinner your roof gets.

Digging is the whole game. You walk left and right and fall when there is nothing under you, and holding the drill button while pressing a direction cuts through the soil below, above or to the side. The drill heats up as you use it; let the gauge fill and it overheats, and you have to wait for it to cool down. Gold nuggets are buried along the way, and picking one up also cools the drill a little. Somewhere on each level there is also a power-up: a super drill that cannot overheat, a short spell of invincibility or a magnet that pulls the gold towards you.

You are not alone down there, and each day brings more company. Flies drift around and tend to climb, sliders patrol from side to side, seekers home in when you come close, drones dig through the ground after you, and bombers start a countdown when you get near and blow a hole in everything around them. Every hit costs a heart, and the game shows what hit you.

Between days there is a shop where gold buys an extra heart, a faster drill or a better cooler. A day screen shows the wind and how acidic the rain will be, and both get worse as you go. Survive all seven days and you win; lose your last heart and the run is over, with a summary of what you collected, spent, drilled and survived. Each run gets a new random layout.

Playing it here

ACID RAIN was made for WASM-4, a fantasy console: an imaginary handheld with a 160 by 160 screen, four colours, a D-pad and two buttons, for which independent developers write new games. Mathieu Dombrock wrote it in Rust in 2025, and it runs here in the official WASM-4 runtime. Click Play, press any button after the short intro text, set up the run on the title screen and press X.

The title screen has three settings: the difficulty, in eight steps (MEDIUM by default), automatic or manual drilling, and the mode. ARCADE is the full run of seven days; TRAIN is a calm practice level without enemies or acid that sends you back to the title when you reach the exit; ZOMBIE is the full run but you cannot die. Z changes the colour palette, with eleven to choose from.

Runs are not saved, but Enter opens the WASM-4 menu, where you can save and load the state while the page is open (2 and 4 do the same directly). A gamepad works too, and on touch screens an on-screen D-pad and buttons appear.

Controls

With automatic drilling, the directions drill on their own and X is not needed. Space, V or the period key also work as X, and C or the comma key as Z.

A few things worth knowing

Dig under, not in the open. A tunnel with a layer of earth above it keeps the rain off for a while. Avoid long walks across the surface, especially on windy days.

Mind the heat gauge. The bar under the hearts is the drill's temperature. Short bursts and a pause now and then beat drilling until it overheats, which can leave you stuck in the open.

Stand on the door to leave. Reaching the exit is not enough: stay on it for about two seconds until the level ends.

Spend on hearts first. You start with four hearts out of a possible eight, and a heart costs half as much as the drill upgrades.

Credits and licence

ACID RAIN was created by Mathieu Dombrock, who wrote the code, drew the graphics and composed the short tunes, all inside the program. It is free software under the GNU General Public License, version 3. The compiled game also contains the Rust libraries buddy-alloc and fastrand (MIT licence) and the WASM-4 bindings (ISC licence), and it runs here in the WASM-4 runtime (ISC licence). The licence texts and the source code of the build served here, with the script used to compile it, are linked from this page.