/* UK Home Energy Calculators — "energy label" design
   Signature: EPC-style rating arrows. Everything else stays quiet. */
:root{
  --paper:#f6f8f9; --surface:#ffffff; --ink:#14213d; --ink-2:#4a5672; --rule:#d5dbe3; --field:#eef1f5;
  --band:#14213d; --band-ink:#ffffff; --band-dim:#aab4c8;
  --a:#008054; --b:#19b459; --c:#8dce46; --d:#ffd500; --e:#fcaa65; --f:#ef8023; --g:#e9153b;
  --good:#008054; --warn-bg:#fff4e8; --warn-ink:#9a4a0b;
  --display:'Archivo', system-ui, sans-serif;
  --text:'Source Serif 4', Georgia, serif;
  --measure:66ch;
}
@media (prefers-color-scheme: dark){
  :root{
    --paper:#0d1526; --surface:#15203a; --ink:#e9edf5; --ink-2:#a3aec4; --rule:#29365a; --field:#1c2846;
    --band:#091021; --band-dim:#8592ad; --good:#3fcf8e; --warn-bg:#3a2611; --warn-ink:#ffb470;
  }
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--paper);color:var(--ink);font:400 16px/1.5 var(--display);-webkit-font-smoothing:antialiased}
a{color:inherit}
:focus-visible{outline:3px solid var(--d);outline-offset:2px;border-radius:4px}

/* ---------- top band ---------- */
.band{background:var(--band);color:var(--band-ink)}
header{max-width:1040px;margin:0 auto;padding:22px 20px 26px;display:grid;gap:24px;align-items:end}
.site{display:inline-flex;align-items:center;gap:10px;text-decoration:none;color:var(--band-ink);font-weight:700;font-size:.95rem;font-stretch:110%;font-variation-settings:'wdth' 110}
.site svg{width:22px;height:22px;flex:none}
.crumbs{margin:18px 0 0;font-size:.85rem;color:var(--band-dim)}
.crumbs a{color:var(--band-dim);text-decoration-color:rgba(255,255,255,.3)}
header h1{margin:14px 0 0;font-weight:800;font-stretch:118%;font-variation-settings:'wdth' 118;font-size:clamp(2rem,6.4vw,3.4rem);line-height:1.02;letter-spacing:-.01em;max-width:16ch}
.crumbs + h1{margin-top:6px}
header .lead{margin:14px 0 0;color:var(--band-dim);font-size:1.05rem;max-width:56ch}
.updated{margin:14px 0 0;font-size:.82rem;color:var(--band-dim)}
.updated b{color:var(--band-ink);font-weight:600}

/* decorative EPC ladder (hub) */
.ladder{display:flex;flex-direction:column;gap:5px;width:min(100%,300px)}
.ladder span{display:flex;align-items:center;height:26px;padding-left:10px;color:#fff;font-weight:800;font-stretch:120%;font-variation-settings:'wdth' 120;font-size:.9rem;clip-path:polygon(0 0,calc(100% - 13px) 0,100% 50%,calc(100% - 13px) 100%,0 100%);transform-origin:left;animation:grow .7s cubic-bezier(.2,.7,.2,1) both}
.ladder span:nth-child(1){width:34%;background:var(--a)}
.ladder span:nth-child(2){width:44%;background:var(--b);animation-delay:.05s}
.ladder span:nth-child(3){width:54%;background:var(--c);animation-delay:.1s;color:#14213d}
.ladder span:nth-child(4){width:64%;background:var(--d);animation-delay:.15s;color:#14213d}
.ladder span:nth-child(5){width:74%;background:var(--e);animation-delay:.2s;color:#14213d}
.ladder span:nth-child(6){width:86%;background:var(--f);animation-delay:.25s}
.ladder span:nth-child(7){width:100%;background:var(--g);animation-delay:.3s}
@keyframes grow{from{transform:scaleX(0)}to{transform:scaleX(1)}}
@media (max-width:759px){.ladder{display:none}}
@media (min-width:760px){
  header.hero{grid-template-columns:1fr 300px;padding-top:28px;padding-bottom:40px}
}
@media (prefers-reduced-motion:reduce){.ladder span{animation:none}}

/* ---------- tabs ---------- */
nav{position:sticky;top:0;z-index:5;background:var(--band);border-top:1px solid rgba(255,255,255,.08)}
nav .tabs{max-width:1040px;margin:0 auto;display:flex;gap:2px;overflow-x:auto;padding:0 12px;scrollbar-width:none}
nav .tabs::-webkit-scrollbar{display:none}
nav a{flex:0 0 auto;text-decoration:none;color:var(--band-dim);font-weight:600;font-size:.92rem;padding:13px 10px 11px;border-bottom:3px solid transparent}
nav a:hover{color:var(--band-ink)}
nav a[aria-current="page"]{color:var(--band-ink);border-bottom-color:var(--d)}

/* ---------- calculator layout ---------- */
main{max-width:1040px;margin:0 auto;padding:28px 16px 40px}
.grid{display:grid;grid-template-columns:1fr;gap:20px;align-items:start}
@media (min-width:860px){.grid{grid-template-columns:minmax(0,1.05fr) minmax(0,.95fr)}}
.card{background:var(--surface);border:1px solid var(--rule);border-radius:6px;padding:20px}
.card h2{margin:0 0 14px;font-size:1.05rem;font-weight:700;font-stretch:110%;font-variation-settings:'wdth' 110;letter-spacing:0}
.card h3{margin:22px 0 10px;padding-top:16px;border-top:1px solid var(--rule);font-size:.95rem;font-weight:700}

/* results card reads like a label: dark header strip */
.grid > .card:last-child{padding:0 18px 18px;overflow:hidden;border-color:var(--ink);border-width:2px}
@media (min-width:860px){.grid > .card:last-child{position:sticky;top:64px}}
.grid > .card:last-child > h2{margin:0 -18px;background:var(--ink);color:var(--paper);padding:11px 18px;font-size:.95rem}

.fields{display:grid;grid-template-columns:1fr 1fr;gap:12px 14px;align-items:end}
label{display:flex;flex-direction:column;gap:5px;font-size:.84rem;font-weight:500;color:var(--ink-2)}
label.full{grid-column:1/-1}
.inp{display:flex;align-items:center;background:var(--field);border:1px solid transparent;border-bottom:2px solid var(--rule);border-radius:4px 4px 0 0;transition:border-color .15s}
.inp span{padding:0 10px;color:var(--ink-2);font-size:.82rem;white-space:nowrap}
.inp:focus-within{border-bottom-color:var(--a);background:var(--surface);border-color:var(--rule) var(--rule) var(--a)}
input,select{width:100%;min-width:0;border:0;background:transparent;color:var(--ink);font:600 1rem var(--display);font-variant-numeric:tabular-nums;padding:10px}
input:focus,select:focus{outline:none}
input[type=time]{font-weight:600}

/* headline figure + supporting figures */
.big{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:0;margin-top:18px;margin-bottom:6px;border-bottom:1px solid var(--rule)}
.stat{padding:0 0 14px}
.stat + .stat{padding-left:12px}
.stat .k{font-size:.8rem;color:var(--ink-2)}
.stat .v{font-weight:700;font-stretch:105%;font-variation-settings:'wdth' 105;font-size:1.2rem;line-height:1.2;margin-top:3px;font-variant-numeric:tabular-nums}
.stat.hl{grid-column:1/-1;order:-1;padding:0 0 14px;margin-bottom:14px;border-bottom:1px solid var(--rule)}
.stat.hl + .stat, .big > .stat:first-child{padding-left:0}
.stat.hl .k{font-size:.9rem;font-weight:600;color:var(--ink)}
.stat.hl .v{font-size:clamp(2.6rem,9vw,3.6rem);font-weight:800;font-stretch:118%;font-variation-settings:'wdth' 118;letter-spacing:-.02em;color:var(--good);line-height:1}

/* EPC arrows for comparisons */
.bars{display:flex;flex-direction:column;gap:7px;margin:16px 0 4px}
.arrow{position:relative;display:flex;align-items:center;justify-content:space-between;gap:10px;min-width:max-content;height:38px;padding:0 26px 0 12px;background:var(--c-arrow,#8dce46);color:var(--c-ink,#fff);font-weight:700;font-size:.95rem;clip-path:polygon(0 0,calc(100% - 16px) 0,100% 50%,calc(100% - 16px) 100%,0 100%);width:var(--w,100%);transition:width .35s cubic-bezier(.2,.7,.2,1)}
.arrow b{font-weight:800;font-stretch:112%;font-variation-settings:'wdth' 112;font-variant-numeric:tabular-nums}
@media (prefers-reduced-motion:reduce){.arrow{transition:none}}

table{width:100%;border-collapse:collapse;font-size:.9rem;font-variant-numeric:tabular-nums;margin-top:14px}
td{padding:8px 0;border-bottom:1px solid var(--rule);vertical-align:top}
td:last-child{text-align:right;font-weight:700;padding-left:12px;white-space:nowrap}
td small{color:var(--ink-2);font-weight:400}
tr:last-child td{border-bottom:0}
.note{font-size:.84rem;color:var(--ink-2);margin-top:14px;padding-top:12px;border-top:1px solid var(--rule)}
.alert{display:none;background:var(--warn-bg);color:var(--warn-ink);border-left:4px solid var(--f);padding:10px 12px;font-size:.88rem;margin-top:14px}
.alert.show{display:block}

/* tariffs editor */
.tariff{border:1px solid var(--rule);border-radius:4px;padding:12px;margin-bottom:10px;background:var(--surface)}
.tariff .head{display:flex;gap:8px;align-items:center;margin-bottom:10px}
.tariff .head input{font-weight:700;padding:4px 0;border-bottom:1px dashed var(--rule)}
.tariff .head select{width:auto;border:1px solid var(--rule);border-radius:4px;padding:5px 6px;font-size:.82rem;font-weight:500}
button{font:600 .88rem var(--display);border:1.5px solid var(--ink);background:transparent;color:var(--ink);border-radius:4px;padding:8px 14px;cursor:pointer}
button:hover{background:var(--ink);color:var(--paper)}
.x{border:0;padding:2px 8px;margin-left:auto;font-size:1.2rem;color:var(--ink-2)}
.x:hover{background:transparent;color:var(--g)}
.tools{display:flex;gap:8px;flex-wrap:wrap;margin-top:6px}
.partner{margin-top:14px;border:1px dashed var(--rule);border-radius:4px;padding:12px;font-size:.88rem}
.partner .tag{font-size:.78rem;font-weight:600;color:var(--ink-2)}

/* ---------- article ---------- */
.prose{max-width:var(--measure);margin:56px auto 0;font:400 1.08rem/1.65 var(--text)}
.prose h2{font:800 1.55rem/1.15 var(--display);font-stretch:112%;font-variation-settings:'wdth' 112;margin:44px 0 12px;letter-spacing:-.005em}
.prose h3{font:700 1.08rem/1.3 var(--display);margin:28px 0 6px}
.prose p,.prose li{margin:0 0 14px}
.prose ol,.prose ul{padding-left:1.3em}
.prose a{color:var(--a);text-underline-offset:2px}
.prose em{font-style:italic}
.prose .formula{font:500 .95rem/1.5 var(--display);font-variant-numeric:tabular-nums;white-space:pre-wrap;border-left:4px solid var(--a);background:var(--surface);padding:12px 16px;margin:0 0 18px}
.faq{border-top:2px solid var(--ink)}
.faq details{border-bottom:1px solid var(--rule)}
.faq summary{cursor:pointer;list-style:none;display:flex;justify-content:space-between;gap:16px;padding:14px 0;font:700 1rem/1.35 var(--display)}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:'+';font-size:1.3rem;line-height:1;color:var(--ink-2)}
.faq details[open] summary::after{content:'\2212'}
.faq details p{margin:0 0 16px}

/* tool lists (hub + related) */
.toollist{list-style:none;margin:0;padding:0;border-top:2px solid var(--ink)}
.toollist li{border-bottom:1px solid var(--rule)}
.toollist a{display:grid;grid-template-columns:14px 1fr auto;gap:4px 16px;align-items:center;text-decoration:none;padding:18px 4px}
.toollist i{grid-row:1/3;align-self:stretch;width:14px;clip-path:polygon(0 0,100% 50%,0 100%);background:var(--chip)}
.toollist b{font-weight:800;font-stretch:112%;font-variation-settings:'wdth' 112;font-size:1.25rem;line-height:1.2}
.toollist span{grid-column:2;color:var(--ink-2);font:400 .98rem/1.45 var(--text)}
.toollist a::after{content:'';grid-row:1/3;grid-column:3;width:10px;height:10px;border-top:2px solid var(--ink-2);border-right:2px solid var(--ink-2);transform:rotate(45deg)}
.toollist a:hover b{text-decoration:underline;text-underline-offset:3px;text-decoration-thickness:2px}
.toollist.small b{font-size:1.05rem}
.toollist.small a{padding:14px 4px}
.prose .toollist{font-family:var(--display)}
main > .toollist{max-width:var(--measure);margin:8px auto 0}
.prose.flush{margin-top:0}

/* ---------- footer ---------- */
footer{max-width:var(--measure);margin:24px auto 0;padding:22px 16px 48px;border-top:1px solid var(--rule);color:var(--ink-2);font-size:.86rem}
footer p{margin:0 0 10px}
footer a{color:var(--ink-2)}
footer button{font-size:.8rem;padding:5px 10px;margin-left:4px}

/* install prompt */
.install{margin-top:16px}
.install p{margin:0;font-size:.9rem}
header .install button{border-color:var(--d);background:var(--d);color:#14213d}
header .install button:hover{background:transparent;color:var(--d)}
header .install p{color:var(--band-dim)}
header .install b{color:var(--band-ink)}
footer .install{margin:0 0 12px}
footer .install button{margin-left:0}

/* iPhone add-to-home-screen banner */
.ios-banner{position:fixed;left:10px;right:10px;bottom:calc(10px + env(safe-area-inset-bottom));z-index:20;display:flex;gap:12px;align-items:flex-start;background:var(--band);color:var(--band-ink);border-radius:12px;padding:12px 10px 12px 12px;box-shadow:0 8px 28px rgba(9,16,33,.35);transform:translateY(130%);transition:transform .3s cubic-bezier(.2,.7,.2,1);max-width:520px;margin:0 auto}
.ios-banner.on{transform:none}
.ios-banner img{border-radius:9px;flex:none}
.ios-banner p{margin:0;font-size:.88rem;line-height:1.45;color:var(--band-dim);flex:1}
.ios-banner p > b:first-child{display:block;color:var(--band-ink);font-size:.95rem;margin-bottom:2px}
.ios-banner b.inline{color:var(--band-ink)}
.ios-banner .share,.ios-banner .dots{display:inline-flex;align-items:center;justify-content:center;vertical-align:middle;line-height:1;margin-top:-3px;width:24px;height:22px;border-radius:5px;background:rgba(255,255,255,.12);color:#5ea8ff}
.ios-banner .share svg{width:17px;height:17px}
.ios-banner .dots{font-size:.6rem;letter-spacing:1px;width:28px}
.ios-banner .close{flex:none;border:0;background:transparent;color:var(--band-dim);font-size:1.4rem;line-height:1;padding:0 6px}
.ios-banner .close:hover{background:transparent;color:var(--band-ink)}
@media (prefers-reduced-motion:reduce){.ios-banner{transition:none}}