claude-sonnet-5.5 · round 2 of 2 · seed 2$0.01MP4stir.html
stir.html · 23 lines
<!DOCTYPE html><html><head><style>
body{margin:0;background:#d9c7ad;height:100vh;display:flex;align-items:center;justify-content:center}
.s{position:relative;width:400px;height:400px;top:50px}
.saucer{position:absolute;left:30px;top:290px;width:340px;height:70px;border-radius:50%;background:#eee;box-shadow:0 10px 15px #0004,inset 0 -6px 0 #ccc}
.handle{position:absolute;left:285px;top:150px;width:80px;height:100px;border:20px solid #fafafa;border-radius:50%;box-sizing:border-box;box-shadow:inset 0 0 0 2px #ddd}
.cup{position:absolute;left:60px;top:110px;width:260px;height:210px;background:linear-gradient(90deg,#ddd,#fff 30%,#fff 60%,#ccc);border-radius:0 0 130px 130px/0 0 190px 190px;box-shadow:inset -10px -8px 20px #0002}
.rim{position:absolute;left:50px;top:90px;width:280px;height:70px;border-radius:50%;background:#fff;box-shadow:inset 0 -3px 4px #bbb}
.cof{position:absolute;left:60px;top:97px;width:260px;height:56px;border-radius:50%;background:radial-gradient(ellipse,#6b3d1e,#3a1c0a 80%);overflow:hidden}
.sw{position:absolute;left:50%;top:50%;width:150px;height:30px;margin:-15px 0 0 -75px;border-radius:50%;border:3px solid #a8703f;border-color:#a8703f transparent transparent transparent;animation:r 2s linear infinite}
.sw2{width:90px;height:16px;margin:-8px 0 0 -45px;animation-duration:1.4s}
@keyframes r{to{transform:rotate(360deg)}}
.orbit{position:absolute;left:190px;top:125px;width:0;height:0;animation:o 1.6s linear infinite}
@keyframes o{from{transform:translate(-55px,0)}25%{transform:translate(0,9px)}50%{transform:translate(55px,0)}75%{transform:translate(0,-9px)}to{transform:translate(-55px,0)}}
.spoon{position:absolute;left:0;top:0;width:14px;height:175px;transform-origin:50% 100%;margin:-175px 0 0 -7px;transform:rotate(25deg)}
.spoon:before{content:"";position:absolute;left:5px;top:0;width:5px;height:150px;background:linear-gradient(90deg,#999,#eee,#888);border-radius:3px}
.spoon:after{content:"";position:absolute;left:-3px;top:145px;width:20px;height:30px;border-radius:50%;background:radial-gradient(#fff,#aaa)}
.front{position:absolute;left:60px;top:125px;width:260px;height:100px;overflow:hidden;clip-path:inset(0 0 0 0)}
</style></head><body><div class="s">
<div class="saucer"></div><div class="handle"></div><div class="cup"></div><div class="rim"></div>
<div class="cof"><div class="sw"></div><div class="sw sw2"></div></div>
<div class="orbit"><div class="spoon"></div></div>
</div></body></html>
round 1 of 2
A spoon stirring in a cup, in HTML and CSS, by Claude Sonnet 5.5, the render after round 1
12What the model saw after each round. The picture above is the round that was scored, round 2.

A spoon stirring in a cup, in HTML and CSS: Claude Sonnet 5.5

modelanthropic/claude-sonnet-5.5taskcss-stirring-spoon@v1, checks c1, harness h1date2026-10-19rounds2 of 8 allowed, 12 minutes on the clockcost$0.0074thinkingmediumtokens16,940 in, 2,045 out, of which 128 reasoningtime43 s
HTML and CSS onlydecided by a number, from the filepass
A CSS loop that moves somethingdecided by a number, from the filepass
Reads as a cup seen intodecided by looking · someone else could reasonably disagreepass
The spoon does the stirringdecided by looking · someone else could reasonably disagreepass
Reads as inside the cupdecided by looking · someone else could reasonably disagreepass
Handle stays on the bowldecided by looking · someone else could reasonably disagreepass
read the post
its other runs
the prompt it was given
Using only HTML and CSS, with no JavaScript, SVG or images, make a cup of coffee with a spoon stirring round and round inside it.
Frozen at v1. This model got this and nothing else.
ground truth

HTML and CSS alone, a continuous loop, and a cup seen from slightly above. The file is read for the brief and for the loop: an @keyframes rule that changes a position or a transform, named by an element, with the iteration count set to infinite. The picture is four moments of the animation, left to right, taken at 0.4 s, 1.2 s, 2.0 s and 2.8 s. Whether the rim reads as an ellipse seen from above, whether the spoon passes behind the far rim on the back half of its circuit, and whether the handle stays on the bowl are judged by eye from the page the run rendered, with the four frames as a first look. How it is scored, and this run's files on GitHub.