:root{--bg-primary: #ffffff;--bg-secondary: #f8f9fa;--bg-gradient-start: #667eea;--bg-gradient-end: #764ba2;--text-primary: #1f2937;--text-secondary: #6b7280;--text-tertiary: #9ca3af;--border-light: #e5e7eb;--card-shadow: rgba(0, 0, 0, .3);--feature-shadow: rgba(0, 0, 0, .1);--accent-primary: #667eea;--accent-primary-hover: #5568d3;--accent-secondary: #6b7280;--accent-secondary-hover: #4b5563;--accent-success: #10b981;--accent-success-bg: #f0fdf4;--accent-danger: #ef4444;--accent-danger-hover: #dc2626;--input-focus-shadow: rgba(102, 126, 234, .1);--btn-shadow: rgba(102, 126, 234, .4);--error-bg: #fee2e2;--error-text: #991b1b;--transition-time: .2s}[data-theme=dark]{--bg-primary: #1f2937;--bg-secondary: #374151;--bg-gradient-start: #5a67d8;--bg-gradient-end: #6d28d9;--text-primary: #f9fafb;--text-secondary: #d1d5db;--text-tertiary: #9ca3af;--border-light: #4b5563;--card-shadow: rgba(0, 0, 0, .7);--feature-shadow: rgba(0, 0, 0, .3);--accent-primary: #818cf8;--accent-primary-hover: #6366f1;--accent-secondary: #9ca3af;--accent-secondary-hover: #6b7280;--accent-success: #10b981;--accent-success-bg: #064e3b;--accent-danger: #f87171;--accent-danger-hover: #ef4444;--input-focus-shadow: rgba(129, 140, 248, .1);--btn-shadow: rgba(129, 140, 248, .4);--error-bg: #7f1d1d;--error-text: #fecaca}*{margin:0;padding:0;box-sizing:border-box}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Oxygen,Ubuntu,Cantarell,sans-serif;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;background-color:var(--bg-primary);color:var(--text-primary);transition:background-color var(--transition-time),color var(--transition-time)}#app{min-height:100vh;background:linear-gradient(135deg,var(--bg-gradient-start) 0%,var(--bg-gradient-end) 100%);display:flex;align-items:center;justify-content:center;padding:20px;transition:background var(--transition-time)}.container{max-width:800px;width:100%}.card{background:var(--bg-primary);border-radius:12px;box-shadow:0 20px 60px var(--card-shadow);overflow:hidden;transition:background-color var(--transition-time),box-shadow var(--transition-time)}.header{background:linear-gradient(135deg,var(--bg-gradient-start) 0%,var(--bg-gradient-end) 100%);color:#fff;padding:3rem 2rem;text-align:center;display:flex;justify-content:space-between;align-items:flex-start;transition:background var(--transition-time)}.header-content{flex:1}.header h1{font-size:2.5rem;margin-bottom:.5rem;font-weight:700}.subtitle{font-size:1.1rem;opacity:.95}.content{padding:2rem}.features{display:grid;gap:1.5rem}.feature{display:flex;gap:1rem;padding:1rem;background:var(--bg-secondary);border-radius:8px;transition:transform var(--transition-time),box-shadow var(--transition-time)}.feature:hover{transform:translateY(-2px);box-shadow:0 4px 12px var(--feature-shadow)}.icon{width:32px;height:32px;background:var(--accent-success);color:#fff;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:700;flex-shrink:0}.feature-text h3{font-size:1.1rem;margin-bottom:.25rem;color:var(--text-primary);transition:color var(--transition-time)}.feature-text p{font-size:.9rem;color:var(--text-secondary);transition:color var(--transition-time)}.divider{height:1px;background:var(--border-light);margin:2rem 0;transition:background-color var(--transition-time)}.demo{text-align:center;margin:1rem 0}.counter-display{font-size:2rem;font-weight:700;color:var(--text-primary);margin-bottom:1.5rem;transition:color var(--transition-time)}.counter-display span{color:var(--accent-primary);transition:color var(--transition-time)}.button-group{display:flex;gap:1rem;justify-content:center;flex-wrap:wrap}.btn-primary{background:var(--accent-primary);transition:background var(--transition-time)}.btn-primary:hover{background:var(--accent-primary-hover)}.btn-secondary{background:var(--accent-secondary);transition:background var(--transition-time)}.btn-secondary:hover{background:var(--accent-secondary-hover)}.btn{background:var(--accent-primary);color:#fff;border:none;padding:1rem 2rem;font-size:1.1rem;border-radius:8px;cursor:pointer;font-weight:600;transition:background .2s,transform .1s,box-shadow var(--transition-time);box-shadow:0 4px 14px var(--btn-shadow)}.btn:hover{background:var(--accent-primary-hover);transform:translateY(-1px)}.btn:active{transform:translateY(0)}.theme-toggle{background:#fff3;border:2px solid white;color:#fff;padding:.75rem 1.25rem;font-size:1rem;border-radius:8px;cursor:pointer;font-weight:600;transition:background .2s,transform .1s;white-space:nowrap}.theme-toggle:hover{background:#ffffff4d;transform:translateY(-1px)}.theme-toggle:active{transform:translateY(0)}.footer{text-align:center;margin-top:1.5rem}.btn-link{display:inline-flex;align-items:center;gap:.5rem;color:var(--accent-primary);text-decoration:none;font-weight:600;padding:.75rem 1.5rem;border:2px solid var(--accent-primary);border-radius:8px;transition:background var(--transition-time),color var(--transition-time)}.btn-link:hover{background:var(--accent-primary);color:#fff}.todos-section{margin-top:2rem}.todos-title{font-size:1.5rem;font-weight:700;color:var(--text-primary);margin-bottom:1.5rem;transition:color var(--transition-time)}.todos-input-group{display:flex;gap:1rem;margin-bottom:1.5rem;flex-wrap:wrap}.todos-input{flex:1;min-width:200px;padding:1rem;font-size:1rem;border:2px solid var(--border-light);border-radius:8px;font-family:inherit;transition:border-color var(--transition-time),background-color var(--transition-time),color var(--transition-time);background-color:var(--bg-primary);color:var(--text-primary)}.todos-input:focus{outline:none;border-color:var(--accent-primary);box-shadow:0 0 0 3px var(--input-focus-shadow)}.todos-list{display:flex;flex-direction:column;gap:.75rem;margin-bottom:1rem}.todo-item{display:flex;align-items:center;gap:1rem;padding:1rem;background:var(--bg-secondary);border-radius:8px;border-left:4px solid var(--accent-primary);transition:background var(--transition-time),transform var(--transition-time)}.todo-item:hover{background:var(--bg-secondary);transform:translate(4px);filter:brightness(1.1)}.todo-item.todo-completed{border-left-color:var(--accent-success);background:var(--accent-success-bg)}.todo-item.todo-completed .todo-text{text-decoration:line-through;color:var(--text-tertiary)}.todo-checkbox{width:20px;height:20px;cursor:pointer;accent-color:var(--accent-primary);flex-shrink:0}.todo-item.todo-completed .todo-checkbox{accent-color:var(--accent-success)}.todo-text{flex:1;color:var(--text-primary);word-break:break-word;transition:color var(--transition-time)}.btn-delete{background:var(--accent-danger);color:#fff;border:none;padding:.5rem 1rem;font-size:.9rem;border-radius:6px;cursor:pointer;font-weight:600;transition:background var(--transition-time),transform .1s;flex-shrink:0}.btn-delete:hover{background:var(--accent-danger-hover);transform:translateY(-1px)}.btn-delete:active{transform:translateY(0)}.todos-empty{text-align:center;padding:2rem;background:var(--bg-secondary);border-radius:8px;color:var(--text-secondary);font-style:italic;transition:background-color var(--transition-time),color var(--transition-time)}.storage-error{padding:1rem;background:var(--error-bg);border-left:4px solid var(--accent-danger);border-radius:6px;color:var(--error-text);margin-bottom:1rem;transition:background-color var(--transition-time),color var(--transition-time)}.clear-completed-container{text-align:center;padding:1rem 0}@media (max-width: 640px){.header h1{font-size:2rem}.content{padding:1.5rem}.todos-input-group{flex-direction:column}.todos-input{min-width:unset}.todo-item{flex-direction:column;align-items:flex-start}.btn-delete{width:100%}}