He found a stable section and sat down with his back against the railing post and his right wrist in front of him.
His thinking was clearer now. The food from the last chest had helped, and the walk since had given him time to turn the watch over in his head without actively looking at it. He had a rough model of what it did. What he needed was to understand how it did it precisely enough to use it without triggering something he did not intend.
He pressed both indentations. The face lit up.
He took his time with it. No rushing. The arrow in his shoulder made rushing difficult anyway, any quick movement produced a specific consequence, so he had learned in the last few hours to slow down and be deliberate, which was turning out to be useful in other contexts as well.
The list was there again. Rows of symbols and numbers, scrollable with the right indentation. He worked through it methodically this time, trying to build a vocabulary of the symbols rather than just cataloguing their shapes. Some appeared in multiple rows with only the numbers changing, which meant they were categories or types. Some appeared only once. He found the symbol he thought represented water containers and cross-referenced the number beside it with what he was carrying. The integer matched his count. The larger number beside it was different from before.
So the larger number changed. Which meant it was not a fixed quantity. It was a price, or a quantity available, or a value. Something that fluctuated.
He kept reading.
It took him the better part of an hour to find what he was looking for, working in short sessions with the face lit and longer pauses to rest his eyes in the grey ambient light of the bridge. The list was long, far longer than his current inventory could account for, which meant most of it was not his. Other people's items. Other people's quantities and values, all listed in the same grid, accessible to anyone with the same device.
He found something that matched a bandage. The symbol was a long narrow rectangle, and the number beside it indicated multiple units available. He highlighted the row and held the watch, thinking about what the platform required of him.
He understood from watching it the day before that items went on the platform and came off the platform. The platform was the exchange surface. He needed to put something on it that the other party would accept in exchange for the bandage. He did not know how the other party's acceptance worked, whether they were actively agreeing to the trade or whether the system matched offers automatically. He suspected automatic. A market that required real-time agreement from both parties would be slow and unreliable, and whatever had built this watch had not built it to be unreliable.
He needed something to offer.
He looked at his inventory. Food block, no. Water, no. The second square of better cloth from the last chest was still unused. He held it up. Clean, dense, clearly of some quality. Worth something to someone who needed it.
But there was something better.
He reached behind his shoulder with his right hand and found the hem-strip tie holding the dressing in place. Worked it loose carefully, held the dressing pad against the wound with his left elbow pressed inward, and removed the right sleeve from underneath. The sleeve was blood-stained from the entry wound, dark brown in patches now, stiff in the way cloth went stiff when blood dried into it. He held it in front of him. Approximately sixty centimetres of tracksuit material with biological evidence of injury. Specific evidence. The kind that told whoever received it something about where he was and what was happening to him.
He replaced the dressing with the clean cloth square and retied the binding. Better than before. The new material was thicker and the pressure was more even. The shoulder acknowledged the improvement.
He held the old sleeve. He put it on the platform.
Nothing happened for four seconds. He counted.
Then the sleeve compressed. Not torn or crushed, compressed, as if all the space between its fibres was simply removed, layer by layer, from the outside in, until it reached a point and that point pulled inward and was gone. The process took less than two seconds and made no sound.
He looked at the empty platform.
Then the bandage appeared, building outward from a point the same way the platform itself had originally built from a point, geometry assembling in sequence. It was a proper bandage, wound in a cylinder, sealed at both ends. Beside it, pressing out of the air two seconds later, a small block of dried food. Darker than the compressed grain blocks from the chests, denser. He picked both up. The bandage was real. The food was real. He pressed his thumb into the food block and it gave slightly, fibrous.
The trade was done.
He sat with the bandage and thought about how to apply it one-handed to a wound he could not see, with an arrow shaft in the way. It took him twenty minutes and produced some language he had not previously known he remembered, but the result was a shoulder dressed properly for the first time, the entry wound covered and padded and the whole thing wrapped firmly enough to stay. He left the arrow in place. The bandage went around it rather than over it, holding the wound stable without disturbing the shaft.
He ate the dried food. It tasted of something he could not name, slightly sweet, and it sat differently in his stomach than the grain blocks did. He noted that and moved on.
He kept the watch face lit after the trade, browsing rather than looking for anything specific. He wanted to understand the full range of what was available. He had the vocabulary now for maybe a quarter of the symbols on the list, enough to recognise categories. Food. Water. Cloth and materials. Tools, he thought some rows were tools, though he could not identify the specific type from the symbols alone. Medicine, possibly, in a cluster of rows with a recurring symbol he associated with treatment rather than supply.
He was scrolling through the lower sections of the list, which had symbols he had not seen before and numbers that were considerably larger, when a row disappeared.
Not scrolled off the edge. Disappeared. He had not touched anything. He had not selected it or highlighted it or interacted with it in any way. It had been in the list and then it was not, the rows below it moving up a single position to fill the gap, the list carrying on as if the row had never been there.
He stared at the space it had occupied.
He did not immediately scroll the list to close the gap.
Someone had bought it. That was the clean explanation: another user on another bridge somewhere had purchased whatever that row represented, and the quantity had dropped to zero, and the listing had closed. That was possible. That was probably the most likely explanation.
The other explanation was that whoever had listed it was no longer in a position to maintain the listing.
He held the watch and thought about the size of the list. Hundreds of rows, possibly more below the sections he had not reached. Thousands of people, then, or had been thousands of people at some point. All of them on bridges or in corridors or wherever they had started, all of them finding chests and watches and figuring out the same interface he had figured out. All of them somewhere in the same system.
He scrolled back up to the section he understood. The row was gone. The list had closed over it cleanly.
'Keep moving.'
He let the face go dark, stood carefully to spare the shoulder, and walked.
He did not look at the watch again for the rest of that stretch. The list was there if he needed it. He knew how to use it now. What it contained, who it contained, he could think about that later, when there was something useful to do with the thinking.
For now the bridge was in front of him and that was the only thing that mattered.