body{margin:0;font-family:Comic Sans MS,cursive;background:linear-gradient(to right,pink,#add8e6);display:flex;justify-content:center;align-items:center;min-height:100vh}.app{text-align:center}h1{color:purple;margin-bottom:1rem}.board{display:grid;grid-template-columns:repeat(4,60px);grid-template-rows:repeat(4,60px);gap:4px;justify-content:center;padding:10px;background:#fff;border-radius:20px;margin-bottom:1rem}.cell{width:60px;height:60px;border-radius:10px;display:flex;justify-content:center;align-items:center;font-size:1.4rem;font-weight:700;cursor:pointer;color:#fff;-webkit-user-select:none;user-select:none}.block1{background-color:pink}.block2{background-color:plum}.block3{background-color:#add8e6}.block4{background-color:#20b2aa;color:#000}.selected{outline:3px solid darkred}.error{background-color:red!important;color:#fff!important}.numbers button{margin:.3rem;padding:.5rem 1rem;font-size:1rem;border:none;border-radius:10px;background-color:#fff;box-shadow:0 0 5px #0003;cursor:pointer}.controls{margin-top:1rem}.controls button{margin:.5rem;padding:.5rem 1rem;font-size:1rem;border-radius:10px;border:none;background-color:pink;cursor:pointer}.fireworks{position:fixed;top:0;right:0;bottom:0;left:0;background:#000c;z-index:999;color:#fff;font-size:3rem;display:flex;flex-direction:column;justify-content:center;align-items:center}.fireworks button{margin-top:2rem;font-size:1.2rem;background:#fff;color:#000;padding:.5rem 1rem;border:none;border-radius:8px;cursor:pointer}@media (max-width: 500px){.board{grid-template-columns:repeat(4,50px);grid-template-rows:repeat(4,50px)}.cell{width:50px;height:50px;font-size:1.2rem}.numbers button,.controls button{padding:.4rem .7rem;font-size:.9rem;margin:.3rem}h1{font-size:1.5rem}.fireworks{font-size:2rem;text-align:center;padding:1rem}}.fullscreen-btn{margin-top:1rem;padding:.5rem 1rem;font-size:1rem;background-color:#ffe6f0;border:2px solid #ff66b2;border-radius:12px;cursor:pointer}button{transition:all .3s ease}