:root{--primary-color: #3498db;--secondary-color: #2980b9;--highlight-color: #f39c12;--error-color: #e74c3c;--board-border: #34495e;--cell-border: #bdc3c7;--cell-bg: #ffffff;--note-color: #7f8c8d;--original-number-color: #2c3e50;--user-number-color: #3498db;--number-btn-bg: linear-gradient(135deg, #3498db, #2980b9);--number-btn-shadow: 0 4px 6px rgba(0, 0, 0, .1);--number-btn-active: linear-gradient(135deg, #2980b9, #1a5276);--control-btn-bg: linear-gradient(135deg, #34495e, #2c3e50);--control-btn-shadow: 0 4px 6px rgba(0, 0, 0, .15);--control-btn-active: linear-gradient(135deg, #2c3e50, #1a2530);--erase-btn-bg: linear-gradient(135deg, #e74c3c, #c0392b);--hint-btn-bg: linear-gradient(135deg, #f39c12, #d35400);--notes-btn-bg: linear-gradient(135deg, #27ae60, #2ecc71);--undo-btn-bg: linear-gradient(135deg, #8e44ad, #9b59b6);--btn-active-scale: .95;--btn-transition: all .2s ease-in-out;--btn-border-radius: 10px}*{box-sizing:border-box;margin:0;padding:0}body{font-family:Roboto,Arial,sans-serif;background-color:#f5f5f5;color:#333;line-height:1.6;margin:0;padding:0;height:100%;width:100%;position:fixed;overflow:hidden}html{height:100%;width:100%}#app{display:flex;flex-direction:column;height:100%;max-width:600px;margin:0 auto;padding:10px;overflow:hidden}header{text-align:center;margin-bottom:10px}h1{font-size:1.8rem;margin-bottom:10px;color:var(--primary-color)}#game-controls{display:flex;justify-content:space-between;margin-bottom:15px}button{background:var(--primary-color);color:#fff;border:none;border-radius:6px;padding:8px 15px;font-size:14px;font-weight:500;cursor:pointer;touch-action:manipulation;transition:var(--btn-transition);box-shadow:0 2px 4px #0000001a}button:active{transform:scale(var(--btn-active-scale));background-color:var(--secondary-color)}@media (hover: hover){button:hover{filter:brightness(1.05);background-color:var(--secondary-color)}}#timer{display:flex;justify-content:center;align-items:center;font-size:1.2rem;font-weight:700;min-width:70px;padding:4px 8px;background-color:#3498db1a;border-radius:6px;color:var(--primary-color)}#game-container{flex:1;display:flex;flex-direction:column;overflow:hidden;position:relative}#sudoku-board{display:grid;grid-template-columns:repeat(9,1fr);grid-template-rows:repeat(9,1fr);aspect-ratio:1/1;max-height:70vh;width:100%;border:2px solid var(--board-border);margin-bottom:10px;touch-action:none;flex-shrink:1}.cell{display:flex;justify-content:center;align-items:center;font-size:1.5rem;border:1px solid var(--cell-border);background-color:var(--cell-bg);position:relative;touch-action:none}.cell.original{font-weight:700;color:var(--original-number-color)}.cell.user-input{color:var(--user-number-color)}.cell.selected{background-color:#3498db33}.cell.same-number{background-color:#3498db1a}.cell.related{background-color:#3498db0d}.cell.error{color:var(--error-color)}.cell:nth-child(3n){border-right:2px solid var(--board-border)}.cell:nth-child(9n){border-right:none}.cell:nth-child(n+19):nth-child(-n+27),.cell:nth-child(n+46):nth-child(-n+54){border-bottom:2px solid var(--board-border)}.notes-container{display:grid;grid-template-columns:repeat(3,1fr);grid-template-rows:repeat(3,1fr);width:100%;height:100%;font-size:.6rem;color:var(--note-color)}.note{display:flex;justify-content:center;align-items:center}.note.highlighted-note{color:var(--highlight-color);font-weight:700;text-shadow:0 0 1px rgba(243,156,18,.5)}#number-pad{display:grid;grid-template-columns:repeat(5,1fr);gap:10px;width:100%;padding:10px 0 20px;margin-top:auto;flex-shrink:0}.number-btn,.control-btn{position:relative;display:flex;flex-direction:column;justify-content:center;align-items:center;color:#fff;border-radius:var(--btn-border-radius);touch-action:manipulation;transition:var(--btn-transition);box-shadow:var(--number-btn-shadow);overflow:hidden;font-weight:600;-webkit-user-select:none;user-select:none;min-height:50px}.number-btn{background:var(--number-btn-bg);font-size:1.6rem;aspect-ratio:1/1;border-radius:50%}.number-btn:before{content:"";position:absolute;top:0;left:0;width:100%;height:100%;background:radial-gradient(circle at 30% 30%,rgba(255,255,255,.3),transparent);opacity:.8;z-index:1;pointer-events:none}.number-btn:active,.control-btn:active{transform:scale(var(--btn-active-scale));opacity:.9}.control-btn{background:var(--control-btn-bg);font-size:.9rem;padding:8px 5px;display:flex;flex-direction:column;gap:3px}.control-btn .icon{font-size:1.2rem;margin-bottom:2px}.erase-btn{background:var(--erase-btn-bg)}.notes-btn{background:var(--notes-btn-bg)}.hint-btn{background:var(--hint-btn-bg)}.undo-btn{background:var(--control-btn-bg)}.notes-btn.active{background:linear-gradient(135deg,#2ecc71,#27ae60);box-shadow:inset 0 0 10px #0000004d,0 2px 4px #0003;transform:scale(.98)}.control-btn .icon{display:flex;justify-content:center;align-items:center;height:24px;margin-bottom:3px}.control-btn .icon svg{width:20px;height:20px;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;fill:none}.erase-btn .icon:before,.notes-btn .icon:before,.hint-btn .icon:before,.undo-btn .icon:before{content:none}@media (hover: hover){.number-btn:hover,.control-btn:hover{filter:brightness(1.05);transform:translateY(-1px);box-shadow:0 5px 8px #0003}}#number-pad{padding-bottom:max(20px,env(safe-area-inset-bottom,20px))}@media screen and (max-height: 700px){.control-btn .icon svg{width:18px;height:18px}}@media screen and (max-height: 600px){.control-btn .icon svg{width:16px;height:16px}}@keyframes pulse{0%{transform:scale(1)}50%{transform:scale(1.05)}to{transform:scale(1)}}.completed{animation:pulse .5s ease-in-out 3}@keyframes hint-pulse{0%{background-color:var(--highlight-color);color:#fff;transform:scale(1)}50%{background-color:var(--highlight-color);color:#fff;transform:scale(1.1)}to{background-color:var(--cell-bg);transform:scale(1)}}.hint-animation{animation:hint-pulse 1s ease-out}.modal{position:fixed;top:0;left:0;width:100%;height:100%;background-color:#000000b3;display:flex;justify-content:center;align-items:center;z-index:1000;opacity:1;transition:opacity .3s ease}.modal-content{background-color:#fff;padding:25px;border-radius:12px;text-align:center;width:80%;max-width:320px;box-shadow:0 5px 20px #0000004d;transform:translateY(0);transition:transform .3s ease}.modal-title{font-size:1.6rem;margin-bottom:20px;color:var(--primary-color);font-weight:700}.difficulty-btn{width:100%;margin:10px 0;padding:12px;font-size:1.1rem;background:var(--number-btn-bg);border-radius:8px;box-shadow:0 2px 5px #0000001a;transition:all .2s ease}.difficulty-btn:hover{transform:translateY(-2px);box-shadow:0 4px 8px #00000026}.difficulty-btn:active{transform:translateY(0);box-shadow:0 2px 3px #0000001a}.hidden{display:none}@supports (padding-bottom: env(safe-area-inset-bottom)){#app,#number-pad{padding-bottom:calc(15px + env(safe-area-inset-bottom))}}.notes-status-message{position:fixed;top:10px;left:50%;transform:translate(-50%);background-color:#3498dbe6;color:#fff;padding:10px 20px;border-radius:20px;font-weight:700;box-shadow:0 3px 10px #0003;z-index:1000;text-align:center;transition:opacity .5s ease;max-width:90%}.notes-status-message.fade-out{opacity:0}.cell-select-prompt{position:fixed;top:50%;left:50%;transform:translate(-50%,-50%);background-color:#3498dbf2;color:#fff;padding:15px 25px;border-radius:10px;box-shadow:0 5px 15px #0000004d;z-index:1000;text-align:center;transition:opacity .5s ease;max-width:90%}.cell-select-prompt.fade-out{opacity:0}.prompt-content{display:flex;flex-direction:column;align-items:center;gap:10px}.prompt-icon{font-size:24px}.prompt-text{font-weight:700}.notes-btn.active{background:linear-gradient(135deg,#2ecc71,#27ae60);box-shadow:inset 0 0 10px #0000004d,0 2px 4px #0003;position:relative}.notes-status-label{position:absolute;top:-8px;right:-8px;background-color:var(--highlight-color);color:#fff;font-size:.7rem;font-weight:700;border-radius:12px;padding:3px 6px;box-shadow:0 2px 5px #0003;border:2px solid white}@keyframes pulse-border{0%{box-shadow:0 0 #2ecc7166,inset 0 0 10px #0000004d}70%{box-shadow:0 0 0 6px #2ecc7100,inset 0 0 10px #0000004d}to{box-shadow:0 0 #2ecc7100,inset 0 0 10px #0000004d}}.notes-btn.pulsing{animation:pulse-border 2s infinite}.number-btn.notes-mode{background:linear-gradient(135deg,#27ae60,#2ecc71);box-shadow:0 4px 6px #27ae6033}.number-btn.notes-mode:active{background:linear-gradient(135deg,#2ecc71,#27ae60);box-shadow:inset 0 2px 5px #0003}@media (hover: hover){.number-btn.notes-mode:hover{filter:brightness(1.05);background:linear-gradient(135deg,#2ecc71,#27ae60)}}.master-difficulty{border:2px solid #c90000;background:linear-gradient(to bottom,#ff9b9b,#ff5252);position:relative}.master-difficulty:hover{background:linear-gradient(to bottom,#ff5252,#c90000)}.difficulty-content{display:flex;align-items:center;justify-content:center;gap:8px}.warning-icon{font-size:1.2em}.warning-modal{border:2px solid #c90000}.warning-modal .modal-title{color:#c90000;font-weight:700;margin-bottom:20px}.modal-message{margin-bottom:20px;text-align:center}.button-container{display:flex;justify-content:center;gap:20px;margin-top:20px}.confirm-btn{background-color:#c90000;color:#fff;padding:10px 20px;border:none;border-radius:4px;cursor:pointer;font-weight:700}.confirm-btn:hover{background-color:#a70000}.cancel-btn{background-color:#666;color:#fff;padding:10px 20px;border:none;border-radius:4px;cursor:pointer}.cancel-btn:hover{background-color:#555}.impossible-difficulty{border:2px solid #000000;background:linear-gradient(to bottom,#444,#000);color:#fff;position:relative;text-shadow:0 0 5px rgba(255,0,0,.7)}.impossible-difficulty:hover{background:linear-gradient(to bottom,#333,#000);box-shadow:0 0 10px #ff0000b3}.impossible-modal{border:2px solid #000000;background-color:#fff;box-shadow:0 0 15px #ff00004d}.impossible-modal .modal-title{color:#000;font-weight:700;margin-bottom:20px;text-shadow:0 0 5px rgba(255,0,0,.5)}.impossible-btn{background-color:#000;border:1px solid #ff0000;box-shadow:0 0 10px #ff000080}.impossible-btn:hover{background-color:#222;box-shadow:0 0 15px #f00c}