*,*::before,*::after{margin:0;padding:0;box-sizing:border-box}
:root{
  --bg-deep:#0a0a1a;--bg-surface:#111128;--bg-card:#1a1a3e;--bg-card-hover:#222260;
  --accent:#6c5ce7;--accent-light:#a29bfe;--accent-glow:#7c6cff;
  --success:#00e676;--error:#ff5252;--warning:#ffd740;
  --text:#eeeeff;--text2:#9999cc;--text3:#666699;
  --border:rgba(108,92,231,0.2);--r:16px;--rs:10px;--rxs:6px;
  --shadow:0 8px 32px rgba(0,0,0,0.4);
  --font:'Sora',sans-serif;--mono:'Space Mono',monospace;--hand:'Caveat',cursive;
  --ease:0.3s cubic-bezier(0.4,0,0.2,1);
}
html{font-size:16px}
body{font-family:var(--font);background:var(--bg-deep);color:var(--text);min-height:100vh;overflow-x:hidden}
#bgCanvas{position:fixed;inset:0;width:100%;height:100%;z-index:0;pointer-events:none}
.screen{display:none;position:relative;z-index:1;min-height:100vh}
.screen.active{display:flex;flex-direction:column}

/* SVG Icon Sizes */
.icon-xs{width:1em;height:1em;vertical-align:-0.12em;flex-shrink:0}
.icon-sm{width:1.1em;height:1.1em;vertical-align:-0.15em;flex-shrink:0}
.icon-md{width:1.3em;height:1.3em;vertical-align:-0.2em;flex-shrink:0}
.card-icon svg{width:100%;height:100%}

/* ===== iOS 26 GLASS POPUP ===== */
.glass-overlay{position:fixed;inset:0;z-index:500;display:none;align-items:center;justify-content:center;background:rgba(0,0,0,0.55);backdrop-filter:blur(20px);-webkit-backdrop-filter:blur(20px)}
.glass-overlay.show{display:flex}
.glass-popup{
  background:rgba(30,30,68,0.72);backdrop-filter:blur(40px);-webkit-backdrop-filter:blur(40px);
  border:1px solid rgba(255,255,255,0.12);border-radius:32px;
  padding:2.2rem 2rem 1.8rem;max-width:380px;width:90%;text-align:center;
  box-shadow:0 24px 80px rgba(0,0,0,0.5),inset 0 1px 0 rgba(255,255,255,0.08);
  animation:glassPop .5s cubic-bezier(.34,1.56,.64,1)
}
.glass-emoji{font-size:3.5rem;margin-bottom:.5rem}
.glass-title{font-size:1.4rem;font-weight:700;margin-bottom:.4rem}
.glass-desc{font-size:.88rem;color:var(--text2);margin-bottom:1.2rem;line-height:1.5}
.glass-input{
  width:100%;background:rgba(255,255,255,0.06);border:1.5px solid rgba(255,255,255,0.12);
  border-radius:999px;padding:.85rem 1.3rem;font-family:var(--font);font-size:1rem;
  color:var(--text);outline:none;text-align:center;transition:var(--ease);margin-bottom:.3rem
}
.glass-input:focus{border-color:var(--accent);box-shadow:0 0 20px rgba(108,92,231,.25)}
.glass-input::placeholder{color:var(--text3)}
.glass-error{font-size:.78rem;color:var(--error);min-height:1.2rem;margin-bottom:.5rem}
.glass-btn{
  display:block;width:100%;border:none;border-radius:999px;padding:.85rem;
  font-family:var(--font);font-size:.95rem;font-weight:600;cursor:pointer;
  transition:var(--ease);margin-bottom:.5rem
}
.glass-btn-primary{background:var(--accent);color:#fff;box-shadow:0 4px 20px rgba(108,92,231,.35)}
.glass-btn-primary:hover{transform:translateY(-2px);box-shadow:0 6px 25px rgba(108,92,231,.5)}
.glass-btn-ghost{background:transparent;color:var(--text2);border:1px solid rgba(255,255,255,.08)}
.glass-btn-ghost:hover{color:var(--text);border-color:rgba(255,255,255,.2)}
@keyframes glassPop{0%{transform:scale(.8);opacity:0}100%{transform:scale(1);opacity:1}}

/* ===== START SCREEN ===== */
.start-content{display:flex;flex-direction:column;align-items:center;justify-content:center;min-height:100vh;padding:1.5rem;gap:1.5rem}
.logo-container{text-align:center;animation:fadeUp .8s ease-out}
.brain-icon{font-size:3.5rem;display:block;animation:float 3s ease-in-out infinite;filter:drop-shadow(0 0 20px rgba(108,92,231,.5))}
@keyframes float{0%,100%{transform:translateY(0)}50%{transform:translateY(-10px)}}
.title{font-family:var(--mono);font-size:2.2rem;font-weight:700;letter-spacing:-1.5px;line-height:1.15;margin-top:.4rem;background:linear-gradient(135deg,var(--text),var(--accent-light));-webkit-background-clip:text;-webkit-text-fill-color:transparent}
.title-accent{font-size:2.6rem;letter-spacing:-2px;background:linear-gradient(135deg,var(--accent),#ff6b9d);-webkit-background-clip:text;-webkit-text-fill-color:transparent}
.subtitle{font-size:1rem;color:var(--text2);text-align:center;line-height:1.5;animation:fadeUp .8s ease-out .2s both}

.player-info{display:flex;align-items:center;gap:.8rem;background:var(--bg-card);border:1px solid var(--border);border-radius:999px;padding:.5rem 1.2rem;animation:fadeUp .8s ease-out .3s both}
.player-info.hidden{display:none}
.player-name{font-weight:600;font-size:.9rem}
.player-level{font-size:.8rem;color:var(--accent-light);font-family:var(--mono)}

/* Area Selector Tabs */
.area-selector{display:flex;gap:.3rem;background:var(--bg-card);border-radius:999px;padding:.25rem;border:1px solid var(--border);animation:fadeUp .8s ease-out .35s both}
.area-tab{background:transparent;border:none;border-radius:999px;padding:.55rem 1.3rem;font-family:var(--font);font-size:.88rem;font-weight:600;cursor:pointer;transition:var(--ease);color:var(--text3)}
.area-tab:hover{color:var(--text)}
.area-tab.active[data-area="addition"]{background:linear-gradient(135deg,var(--accent),#8b5cf6);color:#fff;box-shadow:0 3px 12px rgba(108,92,231,.3)}
.area-tab.active[data-area="subtraction"]{background:linear-gradient(135deg,#e17055,#d63031);color:#fff;box-shadow:0 3px 12px rgba(214,48,49,.3)}
.hidden{display:none!important}

.technique-cards-sub{grid-template-columns:repeat(2,1fr)!important;max-width:520px!important}

.technique-cards{display:grid;grid-template-columns:repeat(3,1fr);gap:.8rem;width:100%;max-width:720px;animation:fadeUp .8s ease-out .4s both}
.technique-card{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--r);padding:1.2rem;position:relative;overflow:hidden;cursor:pointer;transition:var(--ease)}
.technique-card:hover{transform:translateY(-3px);border-color:var(--accent);box-shadow:0 0 25px rgba(108,92,231,.2)}
.technique-card .card-number{font-family:var(--mono);font-size:2.5rem;font-weight:700;position:absolute;top:-6px;right:8px;color:rgba(108,92,231,.08)}
.technique-card .card-icon{font-size:1.6rem;margin-bottom:.3rem}
.technique-card h3{font-size:.85rem;font-weight:700;margin-bottom:.2rem}
.technique-card p{font-size:.72rem;color:var(--text2);margin-bottom:.4rem}
.technique-card .card-example{font-family:var(--mono);font-size:.65rem;color:var(--accent-light);background:rgba(108,92,231,.08);padding:.3rem .5rem;border-radius:var(--rxs)}

.mode-selector{display:flex;flex-wrap:wrap;gap:.4rem;justify-content:center;animation:fadeUp .8s ease-out .5s both}
.mode-btn{background:var(--bg-card);color:var(--text2);border:1px solid var(--border);border-radius:999px;padding:.5rem 1rem;font-family:var(--font);font-size:.8rem;cursor:pointer;transition:var(--ease)}
.mode-btn:hover{border-color:var(--accent);color:var(--text)}
.mode-btn.active{background:var(--accent);color:#fff;border-color:var(--accent)}

.start-btn{background:linear-gradient(135deg,var(--accent),#ff6b9d);border:none;border-radius:999px;padding:.9rem 2.5rem;font-family:var(--font);font-size:1.1rem;font-weight:700;color:#fff;cursor:pointer;display:flex;align-items:center;gap:.4rem;transition:var(--ease);animation:fadeUp .8s ease-out .6s both;box-shadow:0 4px 20px rgba(108,92,231,.4)}
.start-btn:hover{transform:translateY(-2px) scale(1.02);box-shadow:0 6px 25px rgba(108,92,231,.5)}
.start-btn:active{transform:scale(.97)}

.ranking-link{background:transparent;border:1px solid rgba(255,215,64,.25);border-radius:999px;padding:.6rem 1.5rem;color:var(--warning);font-family:var(--font);font-size:.9rem;cursor:pointer;transition:var(--ease);animation:fadeUp .8s ease-out .7s both}
.ranking-link:hover{background:rgba(255,215,64,.08);border-color:var(--warning);transform:translateY(-2px)}

/* ===== GAME HEADER ===== */
.game-header{display:flex;align-items:center;justify-content:space-between;padding:.8rem 1rem;background:rgba(17,17,40,.92);backdrop-filter:blur(12px);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:10}
.header-left{display:flex;align-items:center;gap:.8rem}
.header-right{display:flex;align-items:center}
.back-btn{background:var(--bg-card);border:1px solid var(--border);color:var(--text);width:36px;height:36px;border-radius:50%;font-size:1.1rem;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:var(--ease)}
.back-btn:hover{background:var(--accent);border-color:var(--accent)}
.score-display{display:flex;align-items:center;gap:.6rem}
.score-item{display:flex;flex-direction:column;align-items:center}
.score-label{font-size:.6rem;color:var(--text3);text-transform:uppercase;letter-spacing:.5px}
.score-value{font-family:var(--mono);font-size:1.1rem;font-weight:700}
.score-value.streak{color:var(--warning)}
.score-divider{width:1px;height:24px;background:var(--border)}

/* Level Progress Bar */
.level-bar-container{padding:.5rem 1rem;background:rgba(17,17,40,.8);border-bottom:1px solid var(--border)}
.level-info{display:flex;align-items:center;justify-content:space-between;margin-bottom:.3rem;font-size:.75rem}
.level-label{font-weight:700;color:var(--warning)}
.level-badge-inline{color:var(--accent-light);font-size:.7rem}
.level-pts{color:var(--text3);font-family:var(--mono);font-size:.7rem}
.level-bar{height:6px;background:var(--bg-card);border-radius:999px;overflow:hidden}
.level-bar-fill{height:100%;background:linear-gradient(90deg,var(--accent),#ff6b9d,var(--warning));border-radius:999px;transition:width .5s cubic-bezier(.4,0,.2,1);min-width:0}

/* Timer */
.progress-ring{position:relative;width:44px;height:44px}
.progress-ring svg{transform:rotate(-90deg);width:100%;height:100%}
.ring-bg{fill:none;stroke:var(--bg-card);stroke-width:4}
.ring-fill{fill:none;stroke:var(--accent);stroke-width:4;stroke-linecap:round;stroke-dasharray:163.36;stroke-dashoffset:0;transition:stroke-dashoffset 1s linear,stroke .3s}
.ring-fill.warning{stroke:var(--warning)}
.ring-fill.danger{stroke:var(--error)}
.timer-text{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;font-family:var(--mono);font-size:.8rem;font-weight:700}

/* ===== GAME MAIN ===== */
.game-main{flex:1;display:flex;flex-direction:column;align-items:center;padding:1rem;gap:1rem;max-width:650px;margin:0 auto;width:100%;position:relative}

.problem-container{width:100%;background:var(--bg-card);border:1px solid var(--border);border-radius:var(--r);padding:1.5rem;text-align:center;position:relative;overflow:hidden}
.problem-container::before{content:'';position:absolute;inset:0;background:radial-gradient(circle at 50% 0%,rgba(108,92,231,.08),transparent 70%);pointer-events:none}
.problem-display{display:flex;align-items:center;justify-content:center;gap:.6rem;font-family:var(--mono);flex-wrap:wrap}
.problem-num{font-size:2.5rem;font-weight:700;background:linear-gradient(135deg,var(--text),var(--accent-light));-webkit-background-clip:text;-webkit-text-fill-color:transparent}
.problem-op{font-size:1.8rem;color:var(--accent);font-weight:700}
.problem-eq{font-size:1.8rem;color:var(--text3)}
.problem-answer{font-size:2.5rem;font-weight:700;color:var(--accent);animation:pulse 1.5s ease-in-out infinite}
@keyframes pulse{0%,100%{opacity:1}50%{opacity:.35}}

.workspace{width:100%;display:flex;flex-direction:column;gap:.8rem}
.whiteboard-container{width:100%;background:#1e1e3a;border:1px solid var(--border);border-radius:var(--r);overflow:hidden}
.whiteboard-header{display:flex;align-items:center;justify-content:space-between;padding:.4rem .8rem;background:rgba(0,0,0,.2);border-bottom:1px solid var(--border)}
.wb-title{font-size:.78rem;color:var(--text2)}
.wb-tools{display:flex;align-items:center;gap:.3rem}
.wb-tool{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--rxs);width:30px;height:30px;font-size:.8rem;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:var(--ease);color:var(--text)}
.wb-tool:hover{border-color:var(--accent)}
.wb-tool.active{background:var(--accent);border-color:var(--accent)}
.color-picker{width:30px;height:30px;border:none;border-radius:var(--rxs);cursor:pointer;background:transparent;padding:1px}
.size-slider{width:50px;accent-color:var(--accent);height:3px;cursor:pointer}
#whiteboard{display:block;width:100%;height:180px;cursor:crosshair;background:radial-gradient(circle,rgba(108,92,231,.02) 1px,transparent 1px);background-size:18px 18px}

.input-area{display:flex;gap:.6rem;align-items:flex-end;flex-wrap:wrap}
.input-wrapper{flex:1;min-width:160px}
.input-label{display:block;font-size:.65rem;color:var(--text3);margin-bottom:.2rem;text-transform:uppercase;letter-spacing:.5px}
.answer-input{width:100%;background:var(--bg-card);border:2px solid var(--border);border-radius:var(--rs);padding:.75rem 1rem;font-family:var(--mono);font-size:1.3rem;color:var(--text);outline:none;transition:var(--ease);-moz-appearance:textfield}
.answer-input::-webkit-outer-spin-button,.answer-input::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}
.answer-input:focus{border-color:var(--accent);box-shadow:0 0 15px rgba(108,92,231,.15)}
.answer-input.correct{border-color:var(--success);box-shadow:0 0 15px rgba(0,230,118,.15)}
.answer-input.wrong{border-color:var(--error);box-shadow:0 0 15px rgba(255,82,82,.15);animation:shake .5s}
@keyframes shake{0%,100%{transform:translateX(0)}20%,60%{transform:translateX(-6px)}40%,80%{transform:translateX(6px)}}

.action-buttons{display:flex;gap:.4rem;align-items:stretch}
.hint-btn{background:var(--bg-card);border:1px solid rgba(255,215,64,.25);border-radius:var(--rs);padding:.6rem .8rem;color:var(--warning);cursor:pointer;font-family:var(--font);font-size:.8rem;transition:var(--ease)}
.hint-btn:hover{background:rgba(255,215,64,.08)}
.hint-btn:disabled{opacity:.35;cursor:not-allowed}
.submit-btn{background:linear-gradient(135deg,var(--accent),#8b5cf6);border:none;border-radius:var(--rs);padding:.6rem 1.4rem;color:#fff;font-family:var(--font);font-size:.95rem;font-weight:600;cursor:pointer;transition:var(--ease);box-shadow:0 3px 12px rgba(108,92,231,.25)}
.submit-btn:hover{transform:translateY(-2px)}
.submit-btn:active{transform:scale(.97)}
.skip-btn{background:transparent;border:1px solid var(--border);border-radius:var(--rs);padding:.6rem .8rem;color:var(--text3);cursor:pointer;font-family:var(--font);font-size:.8rem;transition:var(--ease)}
.skip-btn:hover{border-color:var(--text2);color:var(--text2)}

.hint-display{width:100%;background:rgba(255,215,64,.06);border:1px solid rgba(255,215,64,.2);border-radius:var(--rs);padding:.8rem 1rem;display:none;animation:fadeUp .4s ease-out}
.hint-display.show{display:block}
.hint-content{font-family:var(--hand);font-size:1.2rem;color:var(--warning);line-height:1.4}

/* Feedback */
.feedback-overlay{position:fixed;inset:0;z-index:100;display:none;align-items:center;justify-content:center;background:rgba(0,0,0,.55);backdrop-filter:blur(6px)}
.feedback-overlay.show{display:flex}
.feedback-card{background:var(--bg-card);border-radius:var(--r);padding:2rem;text-align:center;max-width:380px;width:90%;animation:glassPop .4s cubic-bezier(.34,1.56,.64,1);border:1px solid var(--border)}
.feedback-card.correct{border-color:var(--success);box-shadow:0 0 35px rgba(0,230,118,.12)}
.feedback-card.wrong{border-color:var(--error);box-shadow:0 0 35px rgba(255,82,82,.12)}
.feedback-icon{font-size:3.2rem;margin-bottom:.3rem}
.feedback-text{font-size:1.4rem;font-weight:700;margin-bottom:.2rem}
.feedback-pts{font-family:var(--mono);font-size:1.1rem;margin-bottom:.3rem}
.feedback-pts.positive{color:var(--success)}
.feedback-pts.negative{color:var(--error)}
.feedback-detail{font-size:.9rem;color:var(--text2);margin-bottom:.6rem}
.feedback-explanation{font-family:var(--hand);font-size:1.1rem;color:var(--accent-light);line-height:1.4;background:rgba(108,92,231,.06);border-radius:var(--rxs);padding:.6rem}

/* Level Up */
.level-up-overlay{position:fixed;inset:0;z-index:110;display:flex;align-items:center;justify-content:center;background:rgba(0,0,0,.7);backdrop-filter:blur(10px);animation:fadeIn .3s}
.level-up-card{text-align:center;animation:glassPop .5s cubic-bezier(.34,1.56,.64,1)}
.level-up-card .level-number{font-family:var(--mono);font-size:5rem;font-weight:700;background:linear-gradient(135deg,var(--warning),#ff6b9d,var(--accent));-webkit-background-clip:text;-webkit-text-fill-color:transparent;line-height:1}
.level-up-card .level-up-label{font-size:1.3rem;color:var(--warning);font-weight:700}
.level-up-card .level-desc{font-size:.9rem;color:var(--text2)}

/* ===== RANKING ===== */
.ranking-panel{background:var(--bg-surface);border:1px solid var(--border);border-radius:24px;max-width:480px;width:92%;max-height:85vh;display:flex;flex-direction:column;animation:glassPop .4s cubic-bezier(.34,1.56,.64,1);overflow:hidden}
.ranking-header{display:flex;align-items:center;justify-content:space-between;padding:1.2rem 1.5rem;border-bottom:1px solid var(--border)}
.ranking-header h2{font-size:1.2rem}
.ranking-close{background:var(--bg-card);border:1px solid var(--border);color:var(--text);width:32px;height:32px;border-radius:50%;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:var(--ease);font-size:.9rem}
.ranking-close:hover{background:var(--error);border-color:var(--error)}
.ranking-list{flex:1;overflow-y:auto;padding:1rem}
.ranking-loading{text-align:center;color:var(--text3);padding:2rem}
.ranking-empty{text-align:center;color:var(--text3);padding:2rem;font-size:.9rem}
.ranking-item{display:flex;align-items:center;gap:.8rem;padding:.7rem .8rem;border-radius:var(--rs);margin-bottom:.4rem;background:var(--bg-card);border:1px solid transparent;transition:var(--ease)}
.ranking-item:hover{border-color:var(--border)}
.ranking-item.top1{background:linear-gradient(135deg,rgba(255,215,64,.12),rgba(255,107,157,.06));border-color:rgba(255,215,64,.3)}
.ranking-item.top2{background:linear-gradient(135deg,rgba(192,192,192,.08),rgba(108,92,231,.04));border-color:rgba(192,192,192,.2)}
.ranking-item.top3{background:linear-gradient(135deg,rgba(205,127,50,.08),rgba(108,92,231,.04));border-color:rgba(205,127,50,.2)}
.rank-pos{font-family:var(--mono);font-weight:700;font-size:1.1rem;min-width:30px;text-align:center}
.rank-pos.gold{color:#ffd740}.rank-pos.silver{color:#c0c0c0}.rank-pos.bronze{color:#cd7f32}
.rank-info{flex:1}
.rank-name{font-weight:600;font-size:.9rem}
.rank-level{font-size:.7rem;color:var(--text3)}
.rank-score{font-family:var(--mono);font-weight:700;color:var(--accent-light);font-size:.95rem}

/* ===== ANIMATIONS ===== */
@keyframes fadeUp{from{opacity:0;transform:translateY(16px)}to{opacity:1;transform:translateY(0)}}
@keyframes fadeIn{from{opacity:0}to{opacity:1}}

/* ===== MOBILE ===== */
@media(max-width:768px){
  .title{font-size:1.7rem}.title-accent{font-size:2rem}
  .technique-cards{grid-template-columns:1fr;max-width:360px}
  .problem-num{font-size:2rem}
  .game-header{padding:.6rem .8rem}
  .header-left{gap:.5rem}
  .input-area{flex-direction:column}
  .action-buttons{justify-content:center;width:100%}
  .action-buttons .hint-btn,.action-buttons .submit-btn,.action-buttons .skip-btn{flex:1}
  .hide-mobile{display:none}
  .mode-selector{gap:.3rem}
  .mode-btn{padding:.4rem .7rem;font-size:.72rem}
  #whiteboard{height:150px}
  .glass-popup{padding:1.5rem 1.2rem}
}
@media(max-width:380px){
  .title{font-size:1.4rem}.title-accent{font-size:1.6rem}
  .problem-num{font-size:1.6rem}
  .start-content{padding:1rem;gap:1rem}
  .score-display{gap:.4rem}
  .score-value{font-size:.9rem}
}