Kelp strands sprout from their holdfasts on the sand, each on its own beat (the number under it), and grow one row up every beat. The current pushes each growing tip one column left or right, or lets it rise straight. The timelines at the top show every beat of the current: the lower water and, on later looms, the upper water with its own rhythm.
Each time a tip is pushed past a warp post it weaves a crossing: over the post (bright tip) or under it (dim tip). The pattern card (top left, and the marks on the posts) shows every crossing the cloth needs, in which colour, over or under. Kelp that crosses where the card has nothing is wrong too.
Shuttle peg: a strand that grows into it flips between over and under. Comb stone: holds a tip straight for one beat, whatever the current does. Clip shell: ties the strands that grow into it; two tips that meet in one cell must be tied there or they tangle, and a tied strand is safe from sea urchins, which graze any untied strand that touches them. Two crossings through the same gap fray the cloth. Pieces work on every strand that passes, early or late.
Place pieces, press Grow and watch. Drag the timeline to preview any beat; the faint lines show where your plan will grow. Score = pieces placed (lower is better). Weave the whole card for bronze, then silver and gold. A miss shows how much matched and which rows (ticks beside the card). Ghost shows your best plan, Hint places one working piece.
Keys: arrows move the cursor, 1/2/3/4 pick peg, comb, clip, erase, Enter or X places, Space or R grows, [ ] scrub, Z undo, G ghost, H hint, F speed, C clear, Esc looms. Pad: d-pad, A place, B erase, Y grow, X ghost, LB/RB pick a piece, LT/RT scrub, Start looms.