:root{--board-bg: #e6b380;--line-color: #5d4037;--piece-red: #d32f2f;--piece-black: #212121;--selected-glow: 0 0 10px 2px rgba(0, 150, 255, .8);--last-move: rgba(0, 255, 0, .3);--valid-move: rgba(0, 255, 0, .6)}body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background-color:#333;color:#fff;display:flex;flex-direction:column;align-items:center;margin:0;padding:20px;min-height:100vh}h1{margin-bottom:20px;font-family:"Noto Serif TC",serif;font-weight:900;font-size:3em}.game-layout{display:flex;flex-direction:row;gap:40px;align-items:flex-start}.sidebar{display:flex;flex-direction:column;gap:20px;min-width:200px}.controls{display:flex;flex-direction:column;gap:15px;align-items:stretch}button{padding:12px 16px;cursor:pointer;background:#555;color:#fff;border:1px solid #777;border-radius:4px;font-size:16px}button:hover{background:#666}button.active{background:#007bff;border-color:#0056b3}.difficulty-selector{display:flex;align-items:center;justify-content:space-between;background:#444;padding:10px;border-radius:4px;border:1px solid #777}.difficulty-selector label{font-weight:700;margin-right:10px}.difficulty-selector select{padding:5px;border-radius:4px;border:1px solid #777;background:#555;color:#fff;font-size:14px;flex-grow:1}#status{font-size:1.5em;font-family:"Noto Serif TC",serif;font-weight:700;text-align:center;padding:10px;background:#444;border-radius:8px}.board-container{position:relative;width:630px;height:700px;background-color:var(--board-bg);border:5px solid #4e342e;box-shadow:0 10px 20px #00000080;-webkit-user-select:none;user-select:none}.grid-lines{position:absolute;top:35px;left:35px;width:560px;height:630px;border:2px solid var(--line-color);box-sizing:border-box;z-index:0}.h-line{position:absolute;background:var(--line-color);height:1px;width:100%;left:0}.v-line{position:absolute;background:var(--line-color);width:1px;height:100%;top:0}.river{position:absolute;top:280px;left:1px;width:556px;height:68px;background:transparent;display:flex;justify-content:center;align-items:center;color:var(--line-color);font-size:32px;font-family:"Noto Serif TC",serif;z-index:1}.palace-line{position:absolute;background:var(--line-color);height:1px;transform-origin:top left;z-index:0}.piece{position:absolute;width:56px;height:56px;border-radius:50%;background:#f0d9b5;border:2px solid #8d6e63;box-shadow:2px 2px 4px #0006;display:flex;justify-content:center;align-items:center;font-size:36px;font-family:"Noto Serif TC",serif;font-weight:700;cursor:pointer;z-index:10;transition:transform .2s,top .2s,left .2s;transform:translate(-50%,-50%)}.piece.red{color:var(--piece-red);border-color:var(--piece-red)}.piece.black{color:var(--piece-black);border-color:var(--piece-black)}.piece.selected{box-shadow:var(--selected-glow);z-index:20}.dot{position:absolute;width:16px;height:16px;background-color:var(--valid-move);border-radius:50%;transform:translate(-50%,-50%);z-index:5;pointer-events:none}.last-move-marker{position:absolute;width:60px;height:60px;pointer-events:none;z-index:2;transform:translate(-50%,-50%)}.last-move-marker:before,.last-move-marker:after,.last-move-marker .corner-bottom-left,.last-move-marker .corner-bottom-right{content:"";position:absolute;width:12px;height:12px;border-color:#2196f3;border-style:solid}.last-move-marker:before{top:0;left:0;border-width:3px 0 0 3px}.last-move-marker:after{top:0;right:0;border-width:3px 3px 0 0}.last-move-marker .corner-bottom-left{bottom:0;left:0;border-width:0 0 3px 3px}.last-move-marker .corner-bottom-right{bottom:0;right:0;border-width:0 3px 3px 0}@media(max-width:900px){.game-layout{flex-direction:column;align-items:center}.sidebar{width:100%;flex-direction:row;justify-content:space-between;align-items:center}.controls{flex-direction:row}}@media(max-width:700px){.board-container{transform:scale(.7);transform-origin:top center;margin-bottom:-210px}.sidebar{flex-direction:column}}@media(max-width:480px){body{padding:10px}h1{font-size:2em;margin-bottom:10px}.board-container{transform:scale(.47);margin-bottom:-370px}}