:root { color-scheme: light; font-family: Inter, system-ui, sans-serif; color: #172033; background: #f2f5f9; }
* { box-sizing: border-box; }
body { margin: 0; }
.lab-banner { padding: .7rem; background: #ffd84d; color: #740b0b; border-bottom: 4px solid #b31313; text-align: center; font-weight: 900; letter-spacing: .04em; }
header { background: #172033; color: white; padding: 1rem max(2rem, calc((100% - 1100px) / 2)); display: flex; gap: 2rem; align-items: center; justify-content: space-between; }
.brand { color: white; font-size: 1.25rem; font-weight: 750; text-decoration: none; }
nav { display: flex; gap: 1rem; align-items: center; flex-wrap: wrap; }
nav a, .link-button { color: #dce7ff; background: none; border: 0; padding: 0; font: inherit; cursor: pointer; text-decoration: none; }
nav form { margin: 0; }
main { max-width: 1100px; margin: 2rem auto; padding: 0 1rem; min-height: 70vh; }
footer { padding: 1.5rem; text-align: center; color: #57637a; }
.card { background: white; border: 1px solid #d9e0ea; border-radius: 10px; box-shadow: 0 2px 8px #1e2b4412; padding: 1.4rem; margin: 1rem 0; }
.narrow { max-width: 480px; margin: 4rem auto; }
.stack { display: grid; gap: 1rem; }
label { display: grid; gap: .4rem; font-weight: 650; }
input, textarea { width: 100%; border: 1px solid #aeb8c7; border-radius: 6px; padding: .75rem; font: inherit; }
button, .button { display: inline-block; border: 0; border-radius: 6px; padding: .7rem 1rem; background: #1559b7; color: white; font-weight: 700; cursor: pointer; text-decoration: none; }
.danger-button { background: #b31313; }
.button.secondary { background: #48566d; }
.actions { display: flex; gap: .75rem; flex-wrap: wrap; margin: 1rem 0; }
.grid, .test-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 1rem; }
.grid .card, .test-grid .card { margin: 0; }
.metric span { display: block; color: #68758b; margin-bottom: .5rem; }
.metric strong { font-size: 1.25rem; }
.muted, .meta { color: #68758b; }
.meta { font-size: .9rem; }
.warning-box, .danger-box { padding: .9rem; border-radius: 6px; background: #fff4ce; border-left: 5px solid #efac00; }
.danger-box { background: #ffe1e1; border-left-color: #c32121; }
.flash { padding: .8rem; border-radius: 6px; background: #dbeaff; }
.flash.error { background: #ffe1e1; }
.flash.success { background: #dff6e6; }
code, pre, .code-output { font-family: ui-monospace, SFMono-Regular, Consolas, monospace; }
pre { overflow-wrap: anywhere; white-space: pre-wrap; background: #eef2f7; padding: .75rem; border-radius: 5px; }
.code-output { font-size: .85rem; white-space: pre; }
.feedback-body { border-top: 1px solid #e1e6ee; padding-top: 1rem; }
@media (max-width: 760px) { header { align-items: flex-start; flex-direction: column; } }