:root{--bg:#0f1117;--sf:#1a1d27;--sf2:#222635;--bd:#2e3347;--tx:#e2e4ed;--txm:#8b8fa7;--list:#22d3ee;--set:#a78bfa;--que:#34d399;--map:#f472b6;--mix:#60a5fa;--grn:#22c55e;--red:#ef4444;--yel:#eab308;--cbg:#141620}
*{margin:0;padding:0;box-sizing:border-box}
body{background:var(--bg);color:var(--tx);font-family:'DM Sans',sans-serif;line-height:1.7}
.hero{padding:3rem 2rem 2rem;text-align:center;background:linear-gradient(180deg,#161929,var(--bg));border-bottom:1px solid var(--bd);position:relative;overflow:hidden}
.hero::before{content:'';position:absolute;top:-60%;left:50%;transform:translateX(-50%);width:600px;height:600px;background:radial-gradient(circle,rgba(96,165,250,.08),transparent 70%);pointer-events:none}
.hero h1{font-family:'JetBrains Mono',monospace;font-size:clamp(1.6rem,4vw,2.4rem);font-weight:700;letter-spacing:-.5px;margin-bottom:.5rem;position:relative}
.hero h1 span{color:var(--mix)}
.hero p{color:var(--txm);font-size:1rem;max-width:560px;margin:0 auto}
.legend{display:flex;flex-wrap:wrap;justify-content:center;gap:1rem;margin-top:1.5rem}
.legend-item{display:flex;align-items:center;gap:.4rem;font-size:.8rem;color:var(--txm)}
.legend-dot{width:10px;height:10px;border-radius:50%}
.tabs{display:flex;justify-content:center;gap:.5rem;padding:1.5rem 1rem 0;flex-wrap:wrap}
.tab-btn{padding:.5rem 1.2rem;border:1px solid var(--bd);border-radius:8px;background:var(--sf);color:var(--txm);font-family:'JetBrains Mono',monospace;font-size:.82rem;cursor:pointer;transition:all .2s}
.tab-btn:hover{border-color:var(--mix);color:var(--tx)}
.tab-btn.active{background:var(--mix);color:var(--bg);border-color:var(--mix);font-weight:600}
.container{max-width:900px;margin:0 auto;padding:1.5rem 1.5rem 4rem}
.exercise{background:var(--sf);border:1px solid var(--bd);border-radius:12px;margin-bottom:1.5rem;overflow:hidden;display:none;animation:fadeIn .3s ease}
.exercise.visible{display:block}
@keyframes fadeIn{from{opacity:0;transform:translateY(8px)}to{opacity:1;transform:none}}
.ex-header{padding:1.2rem 1.5rem;display:flex;align-items:center;gap:1rem;cursor:pointer;user-select:none;transition:background .15s}
.ex-header:hover{background:var(--sf2)}
.ex-num{font-family:'JetBrains Mono',monospace;font-weight:700;font-size:.75rem;padding:.25rem .6rem;border-radius:6px;white-space:nowrap;flex-shrink:0}
.ex-title{flex:1;font-weight:600;font-size:.95rem}
.diff{font-size:.7rem;font-family:'JetBrains Mono',monospace;padding:.2rem .5rem;border-radius:4px;text-transform:uppercase;letter-spacing:.5px;flex-shrink:0}
.d-e{background:rgba(34,197,94,.15);color:var(--grn)}
.d-m{background:rgba(234,179,8,.15);color:var(--yel)}
.d-h{background:rgba(239,68,68,.15);color:var(--red)}
.chv{width:20px;height:20px;color:var(--txm);transition:transform .25s;flex-shrink:0}
.exercise.open .chv{transform:rotate(180deg)}
.ex-body{max-height:0;overflow:hidden;transition:max-height .4s ease}
.exercise.open .ex-body{max-height:5000px}
.ex-content{padding:0 1.5rem 1.5rem;border-top:1px solid var(--bd)}
.ex-content h4{font-family:'JetBrains Mono',monospace;font-size:.78rem;color:var(--txm);text-transform:uppercase;letter-spacing:1px;margin:1.2rem 0 .6rem}
.ex-content p,.ex-content li{font-size:.9rem;line-height:1.8}
.ex-content ul{padding-left:1.2rem;margin-bottom:.5rem}
.ex-content ul li::marker{color:var(--txm)}
pre{background:var(--cbg);border:1px solid var(--bd);border-radius:8px;padding:1rem 1.2rem;overflow-x:auto;font-family:'JetBrains Mono',monospace;font-size:.8rem;line-height:1.65;margin:.5rem 0;color:#c9cce0}
.k{color:#c084fc}.t{color:#22d3ee}.s{color:#34d399}.c{color:#5c6078;font-style:italic}.n{color:#fb923c}.a{color:#fbbf24}
.hint-btn,.sol-btn{display:inline-flex;align-items:center;gap:.4rem;margin-top:.5rem;padding:.4rem .9rem;border-radius:6px;font-family:'JetBrains Mono',monospace;font-size:.75rem;cursor:pointer;transition:all .2s;margin-right:.5rem}
.hint-btn{background:rgba(96,165,250,.1);border:1px solid rgba(96,165,250,.25);color:var(--mix)}
.hint-btn:hover{background:rgba(96,165,250,.2)}
.sol-btn{background:rgba(34,197,94,.1);border:1px solid rgba(34,197,94,.25);color:var(--grn)}
.sol-btn:hover{background:rgba(34,197,94,.2)}
.hint-text,.sol-code{display:none;margin-top:.6rem}
.hint-text{padding:.8rem 1rem;background:rgba(96,165,250,.06);border-left:3px solid var(--mix);border-radius:0 6px 6px 0;font-size:.85rem;color:var(--txm)}
.hint-text.show,.sol-code.show{display:block}
.cat-list .ex-num{background:rgba(34,211,238,.15);color:var(--list)}
.cat-set .ex-num{background:rgba(167,139,250,.15);color:var(--set)}
.cat-queue .ex-num{background:rgba(52,211,153,.15);color:var(--que)}
.cat-map .ex-num{background:rgba(244,114,182,.15);color:var(--map)}
.cat-mixed .ex-num{background:rgba(96,165,250,.15);color:var(--mix)}
.score-bar{position:fixed;bottom:0;left:0;right:0;background:var(--sf);border-top:1px solid var(--bd);padding:.7rem 1.5rem;display:flex;align-items:center;justify-content:center;gap:1.5rem;font-family:'JetBrains Mono',monospace;font-size:.8rem;z-index:100;backdrop-filter:blur(10px)}
.score-bar span{color:var(--txm)}.score-bar strong{color:var(--mix)}
@media(max-width:600px){.container{padding:1rem 1rem 4rem}.ex-content{padding:0 1rem 1rem}pre{font-size:.72rem;padding:.8rem}.tabs{gap:.35rem}.tab-btn{padding:.4rem .8rem;font-size:.75rem}}