HALFLIGHT

Everything in the vault is decaying. That is what pays you.

You run a containment vault. Every gram you hold is an unstable isotope with a real half-life: it is leaving while you watch, it pays you because it is leaving, and when it goes it transmutes into a daughter that pays differently and runs hotter. You never own a resource. You own a position in a decay chain.

Three systems, and they fight each other

• DECAY — 43 isotopes across 5 chains. Every charge becomes something else under you, on its own schedule.
• CONTAINMENT — shielding gates which isotopes you may hold at all; cooling bills you credits every second you hold them. Safety is a running expense.
• ADJACENCY — inert ballast earns nothing and absorbs heat only from orthogonal neighbours, so the right move is often to spend a whole cell on zero income.

What that feels like

• The vault is a placement puzzle where the profitable layout and the survivable layout are rarely the same one.
• A breach is not instant death. It is a crisis with a timer you can still trade against.
• A meltdown keeps your research tier, unlocked cells, shielding and cooling. It clears material and contamination only — it is never a full restart.
• Autosaves every three seconds and on every purchase. Close the tab; the vault is still there.

How it is built

• No PNG holds a picture of an isotope. A cell’s glow, its emission particles, its spectrometer trace and its codex entry are all computed from the same numbers the economy runs on — 43 isotopes, 121 generated emission spectra.
• Seven hand-authored seamless material plates: vault plating, riveted housing, hazard chevrons, louvres, corrosion, cast lead, sensor scan. Which plate a cell wears is a readout — cast lead when shielded, hazard scorching through when it runs hot.
• An original score, Slow Chain: a pedal that never cadences under a line that restarts a third lower each pass. An audible decay chain.
• A geiger click rate driven by the vault’s real aggregate decay rate. The sound is a readout, not a loop.
• No CDN, no webfont, no analytics, no ads, no timers, no purchases. It runs with the network off.

Controls: mouse only. Click a cell to select it, click a market row to load it. HELP is on the title screen and in the vault.

---

Made by Core Systems Asset Factory. We also build engine tools and asset packs for developers — see the full catalogue.

More free browser games from CSAF

Every one of these plays in one click. No install, no account, and they all save as you go.

• PRISMHORN — You never cast a spell. You cast a rainbow.
• OTTERBOUND — Six otters, one raft, and a river that never ends the same way twice.
• CHARGE BARGE — Drive a storm-powered ironclad up an insane hostile coastline.
• RUSTBLOOM — You never find the key. You forge it.
• THE LAST FLOCK — Your army is a crowd you shape with movement alone — and it dies.
• BANNERET: SUCCESSION — You never move a knight. You plant a banner.
• STARCHART — Every voyage you fly is inscribed forever. The route you took IS the constellation.

We also make the parts

Core Systems Asset Factory builds pixel-art packs and engine tooling for developers. If you build games as well as play them, these are ours:

• VERDANT 01 — Overworld — 239 tiles and four complete 47-mask autotile sets, for RPG Maker MZ, Tiled and Godot.
• VERDANT 02 — Elevation — 149 tiles of top-down elevation: a 47-mask plateau autotile and a four-band cliff.
• MOURNCREST 02 — The Pale Choir — five cultists, four directions, three-frame walks, at native 64px and 128px.
• VERDANT 00 — free sample pack — 64 tiles with one complete autotile, free, if you want to try them first.

Plus plugins and editor tools for RPG Maker MZ, GameMaker, Unity and Unreal — the full catalogue is here.