Yes. Corefield is free to play in your browser with no download, no install and no account. It runs on desktop and on phones, and your best run is saved locally so you can close the tab and come back to it.

Classic is a three-minute round against fifteen rivals; when time runs out you are ranked by cores, and dying only costs you some cores and a respawn. Battle has no timer - the field shrinks from the start, eliminated drones stay out, and the last one standing wins. Solo Run is two minutes alone on the field, scored purely on how many cores you bank. Your stats from all three feed the skin unlocks.

By playing, not by paying. Lime needs sixty cores in a single Solo Run, Rose a first-place finish in Classic, Mint a top-three finish in Battle, Ivory a Battle win, and Onyx thirty kills across all your rounds. Skins are purely cosmetic. If one is still locked you can also watch a short ad from the menu to unlock the next one.

Boost is a short burst of speed on Space or the BOOST pad. It recharges in about a second and a half, and the bar under the field shows when it is ready. The cooldown is the whole point: if you could hold it forever nobody would ever be caught, so you spend it to escape a fight, to reach a core first, or to get back inside the circle in Battle.

Cores are the steady income and kills are the spike. A core charges into you while you stand on it, so the fastest harvesting is a tight loop between nearby cores rather than long runs across the field. Killing a drone pays much more, and it pays more the higher that drone had climbed. When someone dies their cores spill onto the ground, so cleaning up after a fight you did not even join is often the best minute of a run.

No. The arena is filled with rival drones that hunt, harvest, retreat and level up on their own, so a run plays the same whether anyone else is around. That was a deliberate choice: an .io game that needs a crowd is empty on the day you happen to visit.

Yes, and it is the field that changes rather than the numbers. The arena is full from the first second, but for the first minute every rival in it is a harvester, working cores and running from a fight. Sentinels, raiders and finally hunters filter in over the next couple of minutes, so the pressure climbs without the map ever thinning out. The arena events run on the same clock, and the later ones only appear if you live long enough to meet them.

Six things that happen once per run, on a timer, and each one changes how you play rather than just printing a message. A core surge drops a cluster into one corner. A bounty triples the reward for killing the leader. A field collapse shrinks the safe area and damages anyone outside it. A prime core worth six levels appears under two neutral guns. A magnetic drift pulls every core to the centre. A sensor blackout hides names and health bars for a while. The later ones only appear in a long run.