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.

They have overheated. Every shot adds heat and the bar under the arena shows how much you have built up. If it reaches the top the guns lock, and they stay locked until the heat has dropped most of the way back down - not just below the top. Firing in bursts and breaking off early keeps you out of that hole, and the Heat Sink upgrade cools you faster. The Overdrive card lets you keep firing while overheated, but every shot then costs you hull.

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.

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.