/* Fluorine Journey: inherit all three reading themes. */
.f-lesson{--f-accent:var(--blue,#187ba3);--f-water:#46a5be;--f-hot:#d97547;--f-coal:#383f49;--f-sand:#cdb77b;--f-soft:color-mix(in srgb,var(--f-accent) 7%,var(--white,#fff));line-height:1.75}
.f-lesson .f-lab{border:1px solid var(--line,#d9e5ec);border-radius:18px;padding:24px;margin:24px 0;background:var(--white,#fff)}
.f-lesson .f-lab>h3{margin:4px 0 16px;font-size:1.35rem;line-height:1.45}.f-eyebrow{display:block;font-size:.74rem;font-weight:700;letter-spacing:.1em;color:var(--f-accent);margin-bottom:8px}.f-lesson p{overflow-wrap:anywhere}.f-lesson .f-small{font-size:.83rem;line-height:1.6;opacity:.78}.f-lesson .button{white-space:normal;line-height:1.5;min-height:44px}.f-lesson button:disabled{opacity:.42;cursor:not-allowed}.f-lesson button:focus-visible,.f-lesson input:focus-visible,.f-lesson select:focus-visible{outline:3px solid var(--f-accent);outline-offset:3px}
.f-note{border:1px solid var(--line);border-left:3px solid var(--f-accent);border-radius:10px;padding:15px 18px;margin:16px 0;line-height:1.7;background:var(--f-soft)}.f-warning{border-left-color:var(--f-hot)}.f-note summary{cursor:pointer;font-weight:700}.f-control{display:flex;flex-direction:column;gap:9px;margin:22px 0;min-width:0}.f-control>span{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}.f-control input[type=range]{width:100%;min-height:32px;accent-color:var(--f-accent)}.f-control input[type=number],.f-control select{width:100%;padding:12px;border:1px solid var(--line);border-radius:10px;font:inherit;color:inherit;background:var(--white,#fff)}
.f-eq{font-size:1.08rem;text-align:center;line-height:2.1;padding:18px 6px;overflow-x:auto}.f-frac{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;line-height:1.55;margin:0 .3em;white-space:nowrap}.f-frac>span{padding:3px 9px}.f-frac>span+span{border-top:1px solid currentColor}.f-eq sup .f-frac{font-size:.85em}.f-lesson .element-table{overflow-x:auto}.f-lesson table{width:100%;border-collapse:collapse;line-height:1.6}.f-lesson td,.f-lesson th{text-align:left;padding:12px;border-bottom:1px solid var(--line);vertical-align:top}.f-chart svg,.f13-scene svg{display:block;width:100%;height:auto;margin:auto}.f-chart svg{max-width:680px}.f-chart text{font-size:14px;fill:currentColor}
.f-goals,.f-result-grid,.f-term-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:18px 0}.f-goals>div,.f-result-grid>div,.f-term-grid>div{border:1px solid var(--line);border-radius:12px;padding:16px;background:var(--f-soft);min-width:0}.f-goals p{margin:5px 0;font-size:.94rem}.f-result-grid span,.f-result-grid small,.f-term-grid span{display:block}.f-result-grid span{font-size:.82rem;opacity:.8}.f-result-grid b{display:block;font-size:clamp(19px,2.2vw,28px);line-height:1.4;margin:7px 0;overflow-wrap:anywhere;font-variant-numeric:tabular-nums}.f-result-grid small{font-size:.78rem}.f-term-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.f-term-grid b{display:block;margin-bottom:7px}.f-term-grid span{font-size:.9rem}
.f-journey{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px}.f-path,.f-step-tabs button,.f-calc-tabs button,.f13-reference-grid button,.f13-equipment-tabs button,.f13-speed{font:inherit;color:inherit;background:var(--white,#fff);border:1px solid var(--line);border-radius:11px;cursor:pointer;min-height:44px;text-align:left;padding:12px}.f-path>span{display:block;font-size:.78rem;color:var(--f-accent);font-weight:700}.f-lesson .is-active{border-color:var(--f-accent);background:var(--f-soft);box-shadow:inset 0 0 0 1px var(--f-accent)}.f-step-tabs{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:7px}.f-step-tabs button{display:flex;align-items:center;gap:10px;font-size:.85rem;padding:10px}.f-step-tabs b{display:grid;place-items:center;flex-shrink:0;width:28px;height:28px;border-radius:50%;background:var(--f-soft);color:var(--f-accent)}.f-step-heading{margin-top:28px}.f-step-heading h3{font-size:1.4rem;line-height:1.45}.f-calc-tabs{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:6px;margin:24px 0 16px}.f-calc-tabs button{font-size:.8rem;line-height:1.4;padding:11px 8px}.f-calc-tabs span{display:block;font-size:1.15rem;font-weight:700;margin-bottom:6px;color:var(--f-accent)}.f-explain{padding:22px;border:1px solid var(--line);border-radius:14px;background:var(--f-soft)}.f-explain h4{font-size:1.25rem;margin:4px 0 16px}.f-mass-pair{display:grid;grid-template-columns:1fr auto 1fr;gap:14px;align-items:center;text-align:center}.f-mass-pair>div{border:1px solid var(--line);border-radius:12px;padding:20px 10px;background:var(--white,#fff)}.f-mass-pair span,.f-mass-pair small{display:block}.f-mass-pair b{display:block;font-size:1.7rem;margin:8px 0}.f-summary{padding:20px;border:1px solid var(--line);border-radius:12px;background:var(--f-soft)}
.f13-panel{padding:20px 0}.f13-panel>h4{font-size:1.15rem;line-height:1.5;margin:0 0 16px}.f13-scene{border:1px solid var(--line);border-radius:14px;background:var(--f-soft);padding:8px;margin:18px 0;overflow:hidden}.f13-scene svg{max-width:760px}.f13-scene text{font-family:Arial,sans-serif;font-size:16px;fill:currentColor}.f13-scene .f13-small{font-size:13px}.f13-center{text-anchor:middle}.f13-scene .f13-digits{font-family:monospace;font-size:24px;font-weight:700}.f13-glass{fill:none;stroke:currentColor;stroke-width:2;stroke-opacity:.55}.f13-pipe{fill:none;stroke:currentColor;stroke-width:3;stroke-opacity:.55}.f13-flow{fill:none;stroke:var(--f-accent);stroke-width:5;stroke-dasharray:8 6}.f13-cooling{fill:none;stroke:var(--f-water);stroke-width:5}.f13-coil{fill:none;stroke:var(--f-accent);stroke-width:7;stroke-linecap:round}.f13-device{fill:var(--white,#fff);stroke:currentColor;stroke-opacity:.3}.f13-screen{fill:var(--f-soft);stroke:var(--line)}.f13-furnace{fill:var(--f-hot);fill-opacity:.14;stroke:var(--f-hot);stroke-width:3}.f13-label{fill:var(--white,#fff);stroke:var(--line)}.f13-electrode{fill:var(--white,#fff);stroke:var(--f-accent);stroke-width:2}.f13-electrode.e1{stroke:var(--f-hot)}.f13-electrode.e2{stroke:var(--f-water)}.f13-scene .f13-on-accent{fill:#fff;font-size:12px;font-weight:bold}
.f13-reference-grid{display:flex;flex-wrap:wrap;gap:7px}.f13-reference-grid button{font-size:.85rem;padding:9px 12px}.f13-reference-card{display:grid;grid-template-columns:140px 1fr;align-items:center;gap:20px;margin-top:20px;padding:20px;background:var(--f-soft);border-radius:12px}.f13-reference-card h4{margin:0;font-size:1.12rem}.f13-reference-card p{margin:8px 0 0}.f13-symbol{font-size:clamp(18px,2.8vw,28px);font-weight:700;text-align:center;color:var(--f-accent);overflow-wrap:anywhere}.f13-equipment-tabs{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:8px}.f13-equipment-tabs button{font-size:.87rem;display:flex;gap:10px;align-items:center}.f13-equipment-tabs span{color:var(--f-accent);font-weight:bold}.f13-equipment-body{margin-top:24px}.f13-equipment-body h3{font-size:1.2rem}.f13-checks{display:grid;gap:10px}.f13-checks label{display:flex;gap:12px;align-items:flex-start;padding:13px;border:1px solid var(--line);border-radius:10px}.f13-checks input{margin-top:7px;accent-color:var(--f-accent);width:18px;height:18px;flex-shrink:0}.f13-mass-ledger{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px;font-size:.78rem}.f13-mass-ledger>span{padding:10px;border:1px solid var(--line);border-radius:9px}.f13-mass-ledger b{display:block;font-variant-numeric:tabular-nums;font-size:1rem}.f13-hold{touch-action:none;user-select:none;-webkit-user-select:none}.f13-playback{display:flex;align-items:center;flex-wrap:wrap;gap:8px;margin:18px 0}.f13-speed{padding:7px 12px;text-align:center}.f13-caption{padding:14px 18px;border-radius:10px;background:var(--f-soft)}.f13-status-list{display:flex;flex-direction:column;gap:8px;margin:18px 0;font-size:.9rem}.f13-meter{padding:22px;background:var(--f-soft);border:1px solid var(--line);border-radius:14px;text-align:center}.f13-meter span,.f13-meter small{display:block}.f13-meter b{display:block;font-size:2.6rem;line-height:1.5;font-variant-numeric:tabular-nums}.f13-notice:empty{display:none}.f13-notice{padding:14px 18px;border-left:3px solid var(--f-accent);background:var(--f-soft);border-radius:8px;margin:16px 0}.f13-clean-progress{height:8px;overflow:hidden;border-radius:8px;background:var(--line);margin-top:20px}.f13-clean-progress span{display:block;height:100%;background:var(--f-accent);transition:width .25s ease}.f13-mixing circle{animation:f13-mix .8s ease-in-out}.f13-mixing circle:nth-child(2n){animation-direction:reverse}@keyframes f13-mix{0%{transform:translate(-8px,2px)}35%{transform:translate(14px,-15px)}70%{transform:translate(-10px,-5px)}100%{transform:translate(0,0)}}
@media(max-width:700px){.f-lesson .f-lab{padding:16px}.f-goals,.f-result-grid{grid-template-columns:1fr}.f-term-grid{grid-template-columns:1fr}.f-journey{grid-template-columns:repeat(2,minmax(0,1fr))}.f-step-tabs{grid-template-columns:1fr}.f-calc-tabs{grid-template-columns:1fr}.f-calc-tabs button{display:flex;align-items:center;gap:12px}.f-calc-tabs span{margin:0}.f13-equipment-tabs{grid-template-columns:1fr}.f13-reference-card{grid-template-columns:1fr;gap:8px}.f13-reference-card .f13-symbol{text-align:left}.f13-mass-ledger{grid-template-columns:1fr}.f13-scene{padding:0}.f-explain{padding:15px}.f13-panel .actions{gap:8px}.f13-panel .actions .button{flex:1 1 180px}.f-result-grid b{font-size:24px}.f-lesson td,.f-lesson th{padding:9px}.f-eq{font-size:1rem}}
@media(prefers-reduced-motion:reduce){.f13-mixing circle{animation:none}.f13-clean-progress span{transition:none}}

[data-theme="dark"] .f-lesson{--f-coal:#aeb7c2;--f-sand:#e1c590}