*{box-sizing:border-box}html{min-width:320px}body{margin:0;background:#f6f3ee;color:#1b1535;font:16px/1.5 system-ui,-apple-system,Segoe UI,sans-serif}button{font:inherit;cursor:pointer}button:focus-visible,a:focus-visible{outline:3px solid #6741f4;outline-offset:3px}.challenge-shell{max-width:1120px;margin:auto;padding:clamp(20px,4vw,48px) clamp(16px,4vw,36px) 80px}.eyebrow{color:#6e43f7;font-size:.77rem;font-weight:900;letter-spacing:.17em}.challenge-head h1{font-size:clamp(2.7rem,7vw,5.5rem);line-height:1;margin:.15em 0;letter-spacing:-.065em}.challenge-head h1 em{font-family:Georgia,serif;color:#6b49eb;font-weight:500}.challenge-head p{color:#686477;font-size:1.1rem}.mode-row,.action-row,.controls,.stats{display:flex;gap:10px;flex-wrap:wrap;align-items:center}.mode-row{margin:24px 0}.mode-row button,.action-row button,.controls button,.flag-button{border:2px solid #d9d1ea;border-radius:15px;background:#fff;color:#211a42;padding:12px 17px;font-weight:800;min-height:48px}.mode-row button[aria-pressed=true],.action-row .primary,.flag-button[aria-pressed=true]{background:#21183f;color:#fff;border-color:#21183f}.mode-row button:disabled,.action-row button:disabled{opacity:.5;cursor:default}.stats{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));margin:20px 0;gap:10px}.stats div{background:#fff;border:1px solid #e7e0ee;border-radius:18px;padding:12px 18px}.stats small{display:block;color:#706b80;font-size:.75rem;font-weight:800;letter-spacing:.09em}.stats strong{font-size:1.55rem}.challenge-layout{display:grid;grid-template-columns:minmax(0,1fr) minmax(245px,300px);gap:22px;align-items:start}.board-panel{background:#21183f;border-radius:30px;padding:clamp(15px,3vw,28px);min-width:0;color:#fff;box-shadow:0 16px 36px #21183f25}.board-caption{color:#d4f27b;letter-spacing:.13em;font-size:.75rem;font-weight:900;margin:0 0 14px}.board{display:grid;width:min(100%,540px);margin:0 auto;aspect-ratio:1;touch-action:none;user-select:none;-webkit-user-select:none}.merge-board{grid-template-columns:repeat(4,1fr);gap:clamp(6px,1.5vw,12px);padding:clamp(7px,2vw,14px);background:#57467f;border-radius:20px}.merge-cell{border-radius:13px;background:#3b2d65;display:grid;place-items:center;font-weight:900;font-size:clamp(1.3rem,5vw,3.5rem);font-variant-numeric:tabular-nums;transition:transform .13s,background .13s}.merge-cell:not([data-value="0"]){background:#d7f27c;color:#22213b;animation:appear .18s}.merge-cell[data-value="4"]{background:#9ae5d8}.merge-cell[data-value="8"],.merge-cell[data-value="16"]{background:#ffc270}.merge-cell[data-value="32"],.merge-cell[data-value="64"]{background:#f78ba7}.merge-cell[data-value="128"],.merge-cell[data-value="256"]{background:#b69afc}.merge-cell[data-value="512"],.merge-cell[data-value="1024"],.merge-cell[data-value="2048"]{background:#fff3b5}.sweep-board{grid-template-columns:repeat(8,1fr);gap:clamp(3px,1vw,7px);padding:clamp(5px,1.4vw,10px);background:#483477;border-radius:20px}.sweep-cell{border:0;border-radius:8px;background:#a892e8;color:#21183f;font-size:clamp(.9rem,4.5vw,2rem);font-weight:900;min-width:0;padding:0;aspect-ratio:1;touch-action:manipulation}.sweep-cell:not(.revealed){box-shadow:inset 0 -4px #7763b7}.sweep-cell.revealed{background:#f3eefa;animation:appear .18s}.sweep-cell.flagged{color:#ffcb72}.sweep-cell.hit{background:#ff8ca4}.sweep-cell[data-number="1"]{color:#365cc8}.sweep-cell[data-number="2"]{color:#178e75}.sweep-cell[data-number="3"]{color:#d04e63}.sweep-cell[data-number="4"],.sweep-cell[data-number="5"]{color:#7534bc}@keyframes appear{from{transform:scale(.88)}to{transform:scale(1)}}.controls{justify-content:center;margin:16px auto 5px}.controls button{background:#35285e;color:#fff;border-color:#8171ad;font-size:1.2rem;min-width:64px;min-height:60px;touch-action:manipulation}.controls button:active,.sweep-cell:active{transform:scale(.94)}.board-note{text-align:center;color:#d8cfe9;font-size:.9rem;margin:16px 0 0}.side-panel{background:#fff;border:1px solid #e7e0ee;border-radius:25px;padding:23px}.side-panel h2{margin:8px 0}.side-panel p{color:#686477}.side-panel ul{padding-left:19px}.action-row{margin:18px 0}.status{min-height:3em;font-weight:700;color:#d4f27b;margin:13px 0 0}.challenge-foot{margin-top:26px;color:#706b80}.challenge-foot a{color:#5034be}.flag-button{width:100%;margin:6px 0 14px}.small-note{font-size:.9rem;color:#756e86}@media(max-width:740px){.challenge-layout{grid-template-columns:1fr}.challenge-head h1{font-size:clamp(2.45rem,10vw,4.5rem)}.side-panel{order:2}.stats div{padding:10px}.stats strong{font-size:1.25rem}.board-panel{padding:16px}.controls button{flex:1;min-width:0}.challenge-shell{padding:24px 14px 80px}}@media(max-width:370px){.stats{gap:5px}.stats div{padding:8px}.stats small{font-size:.62rem}.controls{gap:5px}.controls button{padding:8px}}