.tool-directory { padding-bottom: 4rem; }
.tool-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1rem; }
.tool-card { display: flex; flex-direction: column; align-items: flex-start; text-decoration: none; color: var(--text); }
.tool-card h3 { margin: .7rem 0 .2rem; }
.tool-card p { color: var(--muted); margin: 0 0 1rem; }
.tool-icon { display: inline-grid; place-items: center; width: 3rem; height: 3rem; border-radius: 12px; background: var(--deep); color: var(--signal); font: 800 1rem var(--mono); }
.tool-card .arrow { margin-top: auto; color: var(--link); font-weight: 700; }
.tool-note { margin-top: 1.5rem; padding: 1rem 1.2rem; border: 1px solid var(--line); border-left: 3px solid var(--signal); border-radius: var(--radius); background: var(--note-bg); }
.tool-search-label { display: block; font-weight: 700; margin: 1.5rem 0 .4rem; }
.tool-search { width: min(100%, 34rem); font: inherit; padding: .7rem .8rem; border: 1px solid var(--line); border-radius: var(--r-sm); background: var(--bg2); color: var(--text); }
.tool-category { margin-top: 2rem; }
.tool-card-planned { opacity: .72; }
.workbench { padding: clamp(1rem, 3vw, 2rem); }
.workbench-form form { display: grid; gap: 1rem; max-width: 48rem; }
.workbench-form label { display: grid; gap: .4rem; font-weight: 700; }
.workbench-form input, .workbench-form textarea { width: 100%; box-sizing: border-box; font: 1rem var(--mono); padding: .7rem .8rem; border: 1px solid var(--line); border-radius: var(--r-sm); background: var(--bg2); color: var(--text); }
.workbench-list { display: grid; gap: .5rem; margin-top: 1.5rem; max-width: 56rem; }
.workbench-list > div { display: grid; grid-template-columns: minmax(10rem, .7fr) minmax(0, 1.3fr); gap: .7rem; border-bottom: 1px solid var(--line); padding: .7rem 0; }
.workbench-list dt { color: var(--muted); }
.workbench-list dd { margin: 0; overflow-wrap: anywhere; }
.lesson-card { max-width: 56rem; padding: clamp(1rem, 3vw, 2rem); }
.lesson-card pre { overflow: auto; padding: 1rem; background: var(--deep); color: var(--on-deep, #e9f2f5); border-radius: var(--radius); }
.practice-card { max-width: 56rem; padding: clamp(1rem, 3vw, 2rem); }
.practice-card form { display: grid; gap: .6rem; max-width: 32rem; margin: 1rem 0; }
.practice-card input { font: 1rem var(--mono); padding: .7rem .8rem; border: 1px solid var(--line); border-radius: var(--r-sm); background: var(--bg2); color: var(--text); }
.practice-feedback { min-height: 3rem; margin: 1rem 0; padding: .8rem; border-left: 3px solid var(--signal); background: var(--note-bg); }
.table-scroll { overflow-x: auto; margin-top: 1.2rem; }
.table-scroll table { min-width: 620px; }
@media (max-width: 640px) { .workbench-list > div { grid-template-columns: 1fr; gap: .2rem; } }
.tool-page { padding-bottom: 4rem; }
.tool-heading { margin-bottom: 1.5rem; }
.subnet-app { padding: clamp(1rem, 3vw, 2rem); }
.mode-tabs { display: flex; gap: .4rem; border-bottom: 1px solid var(--line); margin-bottom: 1.2rem; }
.mode-tab { border: 0; border-bottom: 3px solid transparent; background: transparent; color: var(--muted); padding: .7rem 1rem; font: inherit; font-weight: 700; cursor: pointer; }
.mode-tab.active { color: var(--text); border-bottom-color: var(--signal); }
.subnet-form label, .subnet-controls label { display: block; font-weight: 700; margin-bottom: .4rem; }
.input-row { display: flex; gap: .6rem; }
.input-row input { flex: 1; min-width: 0; font: 1.1rem var(--mono); padding: .7rem .8rem; border: 1px solid var(--line); border-radius: var(--r-sm); background: var(--bg2); color: var(--text); }
.form-help { margin: .5rem 0 0; font-size: var(--fs-sm); }
.form-error { color: var(--danger, #a92323); font-weight: 700; margin: .7rem 0 0; }
.subnet-controls { margin: 1.4rem 0; padding: 1rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--bg2); }
.subnet-controls output { float: right; font: 700 1.1rem var(--mono); }
.subnet-controls input { width: 100%; accent-color: var(--signal); }
.result-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(360px, 100%), 1fr)); gap: .6rem; }
.result-row { display: grid; grid-template-columns: minmax(8rem, .7fr) minmax(0, 1.3fr); gap: .6rem; align-items: center; border-bottom: 1px solid var(--line); padding: .65rem 0; }
.result-row dt { color: var(--muted); font-size: var(--fs-sm); }
.result-row dd { margin: 0; display: flex; gap: .5rem; align-items: center; min-width: 0; }
.result-row code { overflow-wrap: anywhere; }
.copy-value { margin-left: auto; border: 1px solid var(--line); border-radius: var(--r-sm); background: var(--panel); color: var(--text); padding: .25rem .45rem; cursor: pointer; }
.binary-box { margin-top: 1.2rem; padding: 1rem; background: var(--deep); color: var(--on-deep, #e9f2f5); border-radius: var(--radius); display: grid; gap: .35rem; overflow-x: auto; }
.binary-box code { color: var(--on-deep, #e9f2f5); white-space: nowrap; }
.math-panel { margin-top: 1.5rem; border-top: 1px solid var(--line); padding-top: 1rem; }
.math-panel summary { cursor: pointer; font-weight: 800; }
.subnet-actions { display: flex; flex-wrap: wrap; gap: .6rem; align-items: center; margin-top: 1.4rem; }
@media (max-width: 640px) { .input-row { flex-direction: column; } .input-row .btn { width: 100%; } .result-row { grid-template-columns: 1fr; gap: .2rem; } }