:root{--ink:#102d33;--muted:#68797d;--teal:#0b5b62;--teal-dark:#063f45;--aqua:#1ab5aa;--line:#dce4e2;--green:#18865a;--red:#c4473f}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:radial-gradient(circle at 10% 5%,rgba(26,181,170,.08),transparent 28rem),#f8f8f5;color:var(--ink);font-family:Inter,system-ui,-apple-system,"Segoe UI",sans-serif;-webkit-font-smoothing:antialiased}button,input,select{font:inherit}button{color:inherit}.topbar{height:78px;padding:0 max(28px,calc((100vw - 1180px)/2));display:flex;align-items:center;justify-content:space-between;gap:24px;background:rgba(255,255,255,.92);border-bottom:1px solid var(--line)}
.brand{display:flex;align-items:center;gap:13px;color:var(--ink);text-decoration:none}.brand>span:last-child{display:flex;flex-direction:column}.brand strong{font-size:19px;letter-spacing:-.03em}.brand small{color:var(--muted);font-size:10px;letter-spacing:.08em;text-transform:uppercase}.brand-mark{width:43px;height:43px;border-radius:13px;background:var(--teal);display:flex;justify-content:center;align-items:center;position:relative;box-shadow:0 6px 18px rgba(6,63,69,.18)}.brand-mark i{width:27px;height:13px;border-radius:5px;background:#e9d5a1;position:absolute}.brand-mark i:before,.brand-mark i:after{content:"";width:7px;height:2px;background:#a6d6d2;position:absolute;top:5px}.brand-mark i:before{left:-7px}.brand-mark i:after{right:-7px}.brand-mark b{width:3px;height:15px;z-index:1;margin:0 2px;background:#cf2e2e}.brand-mark b:nth-of-type(2){background:#2864c7}.brand-mark b:nth-of-type(3){background:#c49a2c;margin-left:5px}
.scoreboard{display:flex;align-items:center;gap:9px}.score{min-width:70px;height:47px;padding:6px 11px;border:1px solid var(--line);border-radius:11px;display:flex;flex-direction:column;justify-content:center;background:#fff}.score b{font-size:17px;line-height:1}.score small{font-size:9px;margin-top:4px;text-transform:uppercase;color:var(--muted);letter-spacing:.08em}.score.good b{color:var(--green)}.score.bad b{color:var(--red)}.score.neutral b{color:var(--teal)}.round-button{width:38px;height:38px;border-radius:50%;border:1px solid var(--line);background:#fff;color:var(--muted);cursor:pointer;font-size:20px}.round-button:hover{color:var(--teal);border-color:var(--aqua)}
.hero{min-height:262px;padding:49px max(28px,calc((100vw - 1180px)/2)) 66px;display:flex;align-items:flex-end;justify-content:space-between;gap:32px;color:#fff;background:linear-gradient(100deg,rgba(5,56,62,.97),rgba(6,75,81,.91)),repeating-linear-gradient(120deg,transparent 0 52px,rgba(255,255,255,.04) 53px 54px);position:relative;overflow:hidden}.hero:after{content:"";position:absolute;width:430px;height:430px;border:1px solid rgba(255,255,255,.07);border-radius:50%;right:-80px;top:-265px;box-shadow:0 0 0 70px rgba(255,255,255,.025),0 0 0 140px rgba(255,255,255,.018)}.hero>*{position:relative;z-index:1}.eyebrow{margin:0 0 15px!important;color:#7ce0d7!important;font-size:10px!important;font-weight:800;letter-spacing:.18em}.eyebrow span{display:inline-block;width:20px;height:2px;background:#7ce0d7;vertical-align:middle;margin-right:8px}.hero h1{margin:0;font-family:Georgia,serif;font-size:clamp(36px,5vw,55px);line-height:1.02;font-weight:500;letter-spacing:-.035em}.hero h1 em{color:#9ce8e0}.hero p{margin:15px 0 0;max-width:680px;color:#c4dcdd;font-size:14px;line-height:1.55}.streak{min-width:190px;padding:15px 19px;display:flex;align-items:center;gap:12px;border:1px solid rgba(255,255,255,.18);background:rgba(255,255,255,.08);border-radius:14px}.streak>span{width:36px;height:36px;display:grid;place-items:center;border-radius:50%;background:#e9b93c;color:#083e44;font-size:24px;font-weight:900}.streak div{display:flex;flex-direction:column}.streak small{color:#b8d3d4;font-size:10px;text-transform:uppercase}.streak strong{font-size:14px;margin-top:3px}
.mode-switch{width:min(760px,calc(100% - 40px));min-height:82px;padding:7px;display:grid;grid-template-columns:1fr 1fr;gap:7px;margin:-34px auto 34px;position:relative;z-index:2;background:#fff;border:1px solid var(--line);border-radius:18px;box-shadow:0 16px 38px rgba(18,49,54,.12)}.mode-switch button{border:0;border-radius:13px;background:transparent;padding:12px 16px;display:grid;grid-template-columns:auto 1fr auto;align-items:center;text-align:left;gap:12px;cursor:pointer}.mode-switch button:hover{background:#f1f8f7}.mode-switch button.active{color:#fff;background:var(--teal);box-shadow:0 7px 18px rgba(11,91,98,.22)}.mode-number{width:35px;height:35px;border:1px solid var(--line);border-radius:10px;display:grid;place-items:center;font-family:Georgia,serif;font-size:20px;font-weight:800;background:#f6f8f5}.active .mode-number{color:var(--teal);background:#dff4f1;border-color:transparent}.mode-switch button>span:nth-child(2){display:flex;flex-direction:column}.mode-switch strong{font-size:14px}.mode-switch small{font-size:10px;margin-top:3px;color:var(--muted)}.mode-switch .active small{color:#b9d8da}.mode-switch button>i{width:9px;height:9px;border:2px solid #bec9c7;border-radius:50%;box-shadow:inset 0 0 0 2px #fff;background:#fff}.mode-switch .active>i{background:#5ce0d3;border-color:#5ce0d3}
.workspace-card{width:min(1180px,calc(100% - 40px));margin:auto;display:grid;grid-template-columns:1.25fr .75fr;background:#fff;border:1px solid var(--line);border-radius:21px;overflow:hidden;box-shadow:0 20px 55px rgba(25,54,58,.07)}.resistor-panel,.answer-panel{padding:31px 34px}.resistor-panel{border-right:1px solid var(--line)}.panel-heading{display:flex;justify-content:space-between;align-items:center;gap:20px}.panel-heading>span:first-child{display:flex;flex-direction:column}.panel-heading small{color:#8a999b;font-size:9px;font-weight:800;letter-spacing:.14em}.panel-heading strong{font-family:Georgia,serif;font-size:21px;margin-top:4px}.series-badge{padding:7px 10px;border-radius:20px;color:var(--teal);background:#edf7f5;font-size:10px;font-weight:800;text-transform:uppercase}.step-badge{width:33px;height:33px;border-radius:50%;display:grid;place-items:center;color:var(--teal);border:1px solid #c6d9d7;font-size:10px;font-weight:800}
.resistor-stage{min-height:321px;margin:24px 0 22px;border:1px solid #e0e3dc;border-radius:15px;background:linear-gradient(rgba(14,79,84,.025) 1px,transparent 1px),linear-gradient(90deg,rgba(14,79,84,.025) 1px,transparent 1px),#f5f3e9;background-size:22px 22px;display:flex;align-items:center;flex-direction:column;justify-content:center;overflow:hidden}.orientation{color:#8b948e;font-size:8px;letter-spacing:.14em;font-weight:800;margin-bottom:31px}.orientation span{color:var(--aqua);font-size:16px;margin-right:5px}.resistor{width:min(590px,92%);height:105px;position:relative;display:flex;align-items:center;justify-content:center}.wire{position:absolute;top:50%;width:31%;height:5px;transform:translateY(-50%);background:linear-gradient(#a2a7a5,#e1e3e0 45%,#8a908e)}.wire.left{left:0}.wire.right{right:0}.resistor-body{width:45%;height:84px;border-radius:42% 42% 38% 38%/32% 32% 45% 45%;background:linear-gradient(180deg,#e7d6a9,#cbb581 49%,#b79c69);border:2px solid #9d895f;box-shadow:inset 0 5px 5px rgba(255,255,255,.5),0 8px 15px rgba(81,63,35,.18);position:relative;z-index:1;overflow:hidden}.resistor-body:before,.resistor-body:after{content:"";position:absolute;top:19px;width:12%;height:45px;background:#c3ad7b;z-index:2}.resistor-body:before{left:-4%;border-radius:0 15px 15px 0}.resistor-body:after{right:-4%;border-radius:15px 0 0 15px}.bands{position:absolute;inset:0;z-index:3;display:flex;align-items:stretch}.bands i{display:block;width:9%;height:100%;box-shadow:inset 2px 0 rgba(255,255,255,.16),inset -2px 0 rgba(0,0,0,.13)}.bands-4{gap:7%;padding-left:18%}.bands-4 i:last-child{margin-left:16%}.bands-5{gap:5.5%;padding-left:15%}.bands-5 i:nth-last-child(2),.bands-5 i:last-child{margin-left:5%}.band-labels{margin:28px auto 0;width:min(500px,90%);display:flex;justify-content:center;gap:15px}.band-labels>span{min-width:72px;display:grid;grid-template-columns:12px 1fr;gap:0 6px;align-items:center}.band-labels i{width:11px;height:11px;border-radius:50%;border:1px solid rgba(0,0,0,.12);grid-row:span 2}.band-labels small{font-size:7px;color:#9aa3a1}.band-labels strong{font-size:9px}
.exercise-meta{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}.exercise-meta span{padding:13px 16px;border:1px solid var(--line);border-radius:11px;display:flex;flex-direction:column}.exercise-meta b{font-size:14px;color:var(--teal)}.exercise-meta small{font-size:8px;color:var(--muted);margin-top:3px;text-transform:uppercase}
.answer-panel form{margin-top:27px}.answer-field{display:block;margin-bottom:18px}.answer-field>span:first-child{display:block;margin:0 0 7px;font-size:11px;font-weight:750;color:#41575a}.input-combo{height:47px;display:grid;grid-template-columns:1fr 73px;border:1px solid #ccd8d6;border-radius:9px;overflow:hidden;background:#fff}.input-combo:focus-within{border-color:var(--aqua);box-shadow:0 0 0 3px rgba(26,181,170,.12)}.input-combo input{width:100%;min-width:0;border:0;outline:0;padding:0 13px}.input-combo select{border:0;border-left:1px solid #d7e0de;outline:0;padding:0 8px;background:#f6f8f6;color:var(--teal);font-weight:750}.range-fields{display:grid;grid-template-columns:1fr 1fr;gap:12px}.formula-hint{margin:3px 0 17px;padding:11px 12px;border-radius:8px;background:#f3f7f6;color:#718082;font-size:9px}.formula-hint span{width:17px;height:17px;margin-right:6px;display:inline-grid;place-items:center;border:1px solid #a9bcba;border-radius:50%;color:var(--teal);font-weight:800}.primary-action{width:100%;height:50px;padding:0 18px;border:0;border-radius:9px;display:flex;align-items:center;justify-content:space-between;background:var(--teal);color:#fff;font-size:12px;font-weight:800;cursor:pointer;box-shadow:0 8px 18px rgba(11,91,98,.2)}.primary-action:hover{background:var(--teal-dark)}.primary-action span{font-size:20px}.feedback{margin:0 0 13px;padding:12px;border-radius:10px;display:flex;gap:10px;border:1px solid}.feedback.correct{color:#116b4a;background:#edf8f3;border-color:#b8dfcf}.feedback.incorrect{color:#9b322e;background:#fff1ef;border-color:#ecc5c0}.feedback-icon{width:25px;height:25px;flex:none;border-radius:50%;display:grid;place-items:center;color:#fff;background:currentColor}.feedback>span:last-child{display:flex;flex-direction:column}.feedback strong{font-size:11px}.feedback small{margin-top:3px;font-size:8.5px;color:#586b6d}[hidden]{display:none!important}
.guide-section{width:min(1180px,calc(100% - 40px));margin:25px auto 0;border:1px solid var(--line);border-radius:15px;overflow:hidden;background:#fff}.guide-toggle{width:100%;min-height:66px;padding:12px 19px;border:0;background:#fff;display:flex;justify-content:space-between;align-items:center;cursor:pointer}.guide-toggle>span{display:flex;align-items:center;gap:12px}.guide-toggle>span>b{width:32px;height:32px;display:grid;place-items:center;border-radius:50%;background:#e9f5f3;color:var(--teal)}.guide-toggle>span>span{display:flex;flex-direction:column;align-items:flex-start}.guide-toggle strong{font-family:Georgia,serif;font-size:14px}.guide-toggle small{color:var(--muted);font-size:9px}.guide-toggle>i{width:27px;height:27px;display:grid;place-items:center;font-style:normal;border:1px solid var(--line);border-radius:50%}.color-guide{padding:21px 22px;border-top:1px solid var(--line);display:grid;grid-template-columns:1fr 240px;gap:28px;background:#f8faf8}.color-guide h2{margin:0;font-family:Georgia,serif;font-size:15px}.color-guide p{margin:4px 0 14px;font-size:9px;color:var(--muted)}.color-grid{display:grid;grid-template-columns:repeat(5,minmax(65px,1fr));gap:7px}.color-grid span,.tolerance-guide span{padding:8px;display:grid;grid-template-columns:16px 17px 1fr;align-items:center;gap:5px;border:1px solid var(--line);border-radius:8px;background:#fff}.color-grid i,.tolerance-guide i{width:15px;height:15px;border-radius:4px;border:1px solid rgba(0,0,0,.12)}.color-grid b,.tolerance-guide b{font-size:10px}.color-grid small,.tolerance-guide small{font-size:8px;color:var(--muted)}.tolerance-guide{display:flex;flex-direction:column;gap:8px}.tolerance-guide h2{margin-bottom:7px}.tolerance-guide span{grid-template-columns:20px 1fr auto}footer{width:min(1180px,calc(100% - 40px));margin:22px auto 0;padding:19px 0 32px;display:flex;justify-content:space-between;color:#8a9999;font-size:8px;letter-spacing:.11em}
@media(max-width:900px){.workspace-card{grid-template-columns:1fr}.resistor-panel{border-right:0;border-bottom:1px solid var(--line)}.streak{display:none}.color-guide{grid-template-columns:1fr}}
@media(max-width:640px){.topbar{height:auto;padding:13px 17px;align-items:flex-start}.brand small,.score small,.score.neutral{display:none}.score{min-width:48px;padding:5px 8px}.hero{min-height:228px;padding:38px 20px 58px}.hero h1{font-size:36px}.mode-switch{width:calc(100% - 24px);margin-bottom:21px}.mode-switch button{padding:10px;gap:7px}.mode-switch small,.mode-switch button>i{display:none}.workspace-card,.guide-section,footer{width:calc(100% - 24px)}.resistor-panel,.answer-panel{padding:23px 18px}.resistor-stage{min-height:260px}.resistor{width:112%}.resistor-body{width:52%;height:74px}.band-labels{width:100%;gap:5px}.band-labels>span{min-width:54px}.band-labels strong{font-size:7px}.range-fields{grid-template-columns:1fr;gap:0}.color-grid{grid-template-columns:repeat(2,1fr)}footer{flex-direction:column;gap:7px}}