body{margin:0;font-family:Arial,Helvetica,sans-serif;background:linear-gradient(135deg,#eef2ff,#f8fbff,#eefbf1);color:#1d2a44;}
.container{width:min(1050px,94%);margin:auto;padding:35px 0 50px;}
.topbar{display:flex;justify-content:space-between;gap:20px;background:white;padding:26px;border-radius:24px;margin-bottom:24px;box-shadow:0 18px 45px rgba(31,64,130,.10);}
h1{margin:0 0 8px;font-size:36px;}
.topbar p{margin:0;line-height:1.5;color:#60708f;}
.progress{background:#2451d1;color:white;padding:18px;border-radius:18px;font-weight:bold;font-size:22px;text-align:center;min-width:140px;}
.equation-box{background:#2451d1;color:white;font-size:42px;font-weight:bold;text-align:center;padding:30px;border-radius:24px;margin-bottom:24px;box-shadow:0 18px 45px rgba(36,81,209,.22);}
.example-box,.step-box,.finish-card{background:white;border-radius:22px;padding:24px 28px;margin-bottom:20px;box-shadow:0 14px 35px rgba(31,64,130,.10);border:2px solid rgba(198,213,245,.75);}
.example-box{border-left:8px solid #ffcf33;}
.example-box h2,.step-box h2{margin-top:0;}
.step-box.locked{opacity:.45;}
.answer-row{display:flex;gap:12px;}
input{flex:1;padding:15px;font-size:21px;border-radius:14px;border:2px solid #b8c8ea;}
button{padding:14px 20px;font-size:18px;border:none;border-radius:14px;background:#2451d1;color:white;font-weight:bold;cursor:pointer;}
button:hover:not(:disabled){background:#173fae;}
button:disabled{background:#9caad0;cursor:not-allowed;}
.secondary{background:#eef3fb;color:#2451d1;}
.good{color:#17803b;font-weight:bold;}
.bad{color:#d13232;font-weight:bold;}
.mini-vzor{background:#111827;color:white;padding:12px;border-radius:10px;margin-bottom:10px;font-family:monospace;text-align:center;font-size:17px;}
.step-hint{background:#f3f4f6;border-left:4px solid #3b82f6;padding:10px 14px;border-radius:10px;margin-bottom:12px;}
.footer-buttons{display:flex;justify-content:center;gap:14px;margin-top:26px;}
.finish-card{text-align:center;padding:54px 30px;}
.finish-card p{font-size:22px;color:#60708f;}
@media(max-width:700px){.topbar{flex-direction:column}.answer-row{flex-direction:column}button{width:100%}.equation-box{font-size:30px}}