*{box-sizing:border-box;margin:0;padding:0}body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background-color:#000;color:#fff;line-height:1.6;min-height:100vh}.app-container{max-width:800px;margin:0 auto;padding:2rem;min-height:100vh}.app-header{text-align:center;margin-bottom:3rem;padding:2rem;background:linear-gradient(135deg,#1a1a1a,#2d2d2d);border-radius:12px;border:1px solid #333333;box-shadow:0 8px 32px #0000004d}.app-title{font-size:2.5rem;font-weight:700;margin-bottom:1rem;background:linear-gradient(135deg,#fff,#ccc);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;text-shadow:0 2px 4px rgba(0,0,0,.3)}.app-description{font-size:1.1rem;color:#ccc;margin-bottom:1.5rem;line-height:1.7}.checkbox-container{background-color:#111;border-radius:12px;padding:2rem;border:1px solid #333333;box-shadow:0 4px 24px #0006}.indeterminate-checkbox{display:flex;flex-direction:column;gap:.2rem}.checkbox-item{margin-bottom:.2rem}.checkbox-children{margin-left:2rem;padding-left:1rem;border-left:2px solid #333333;margin-top:.2rem}.checkbox-wrapper{display:flex;align-items:center;gap:.8rem;padding:.3rem 1rem;border-radius:8px;transition:all .3s ease;cursor:pointer;position:relative}.checkbox-wrapper:hover{background-color:#1a1a1a;transform:translate(2px)}.checkbox-input{appearance:none;width:20px;height:20px;border:2px solid #444444;border-radius:4px;background-color:#000;cursor:pointer;position:relative;transition:all .3s ease;flex-shrink:0}.checkbox-input:hover{border-color:#666;box-shadow:0 0 8px #ffffff1a}.checkbox-input:focus{outline:none;border-color:#888;box-shadow:0 0 0 3px #ffffff1a}.checkbox-input:checked{background-color:#fff;border-color:#fff}.checkbox-input:checked:after{content:"✓";position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);color:#000;font-weight:700;font-size:14px}.checkbox-input:indeterminate{background-color:#666;border-color:#666}.checkbox-input:indeterminate:after{content:"−";position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);color:#fff;font-weight:700;font-size:16px}.checkbox-label{font-size:1rem;color:#fff;cursor:pointer;-webkit-user-select:none;user-select:none;transition:color .3s ease;font-weight:500}.checkbox-wrapper:hover .checkbox-label{color:#e0e0e0}.checkbox{margin-left:1rem;padding:.25rem}@media (max-width: 768px){.app-container{padding:1rem}.app-title{font-size:2rem}.checkbox-children{margin-left:1.5rem}.feature-list{text-align:center}}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}.checkbox-item{animation:fadeIn .3s ease-in-out}