*{margin:0;padding:0;box-sizing:border-box}body{margin:0;padding:0;width:100%;min-height:100vh}#root{width:100%}:root{--font-family: "Pretendard", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;--bg-gradient-light: linear-gradient(120deg, #fdfbfb 0%, #ebedee 100%);--card-bg-light: rgba(255, 255, 255, .6);--text-color-light: #263238;--text-secondary-light: #78909c;--accent-color-light: #009688;--accent-gradient-light: linear-gradient(to right, #00bfa5, #009688);--border-color-light: rgba(255, 255, 255, .9);--shadow-light: 0 8px 32px 0 rgba(100, 100, 100, .1);--bg-gradient-dark: linear-gradient(120deg, #0f2027 0%, #203a43 100%);--card-bg-dark: rgba(30, 30, 30, .65);--text-color-dark: #eceff1;--text-secondary-dark: #90a4ae;--accent-color-dark: #26a69a;--accent-gradient-dark: linear-gradient(to right, #26a69a, #80cbc4);--border-color-dark: rgba(255, 255, 255, .1);--shadow-dark: 0 8px 32px 0 rgba(0, 0, 0, .3)}body{font-family:var(--font-family);margin:0;transition:background-color .3s ease}body.light-theme{background:var(--bg-gradient-light);color:var(--text-color-light)}body.dark-theme{background:var(--bg-gradient-dark);color:var(--text-color-dark)}.app-container{display:flex;justify-content:center;align-items:flex-start;min-height:100vh;padding:50px 20px;box-sizing:border-box}.todo-app{width:100%;max-width:550px;padding:30px;border-radius:20px;backdrop-filter:blur(20px);-webkit-backdrop-filter:blur(20px);border:1px solid;box-shadow:var(--shadow-light);transition:all .3s ease}.light-theme .todo-app{background:var(--card-bg-light);border-color:var(--border-color-light);box-shadow:var(--shadow-light)}.dark-theme .todo-app{background:var(--card-bg-dark);border-color:var(--border-color-dark);box-shadow:var(--shadow-dark)}.app-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:25px}.app-header h1{margin:0;font-size:2.5rem;font-weight:800;background-clip:text;-webkit-background-clip:text;color:transparent}.light-theme .app-header h1{background-image:var(--accent-gradient-light)}.dark-theme .app-header h1{background-image:var(--accent-gradient-dark)}.theme-toggle-btn{background:none;border:none;font-size:1.8rem;cursor:pointer;padding:5px;transition:transform .2s ease}.theme-toggle-btn:hover{transform:scale(1.2)}.todo-form{display:flex;gap:10px;margin-bottom:25px}.todo-input{flex-grow:1;padding:15px;font-size:1rem;border:none;border-radius:10px;outline:none;background-color:transparent;border:1px solid;transition:all .3s ease}.light-theme .todo-input{color:var(--text-color-light);border-color:#cfd8dc}.dark-theme .todo-input{color:var(--text-color-dark);border-color:#455a64}.todo-input::placeholder{color:var(--text-secondary-light)}.dark-theme .todo-input::placeholder{color:var(--text-secondary-dark)}.todo-input:focus{box-shadow:0 0 0 2px var(--accent-color-light)}.dark-theme .todo-input:focus{box-shadow:0 0 0 2px var(--accent-color-dark)}.add-btn{padding:15px 25px;font-size:1rem;font-weight:700;border:none;border-radius:10px;color:#fff;cursor:pointer;transition:all .3s ease}.light-theme .add-btn{background-image:var(--accent-gradient-light)}.dark-theme .add-btn{background-image:var(--accent-gradient-dark)}.add-btn:hover{opacity:.9;box-shadow:0 4px 15px #0003}.todo-list{list-style:none;padding:0 10px 0 0;margin:0;max-height:40vh;overflow-y:auto}.todo-item{display:flex;align-items:center;padding:12px 15px;margin-bottom:8px;border-radius:10px;transition:background-color .2s ease;word-break:break-word}.light-theme .todo-item:hover{background-color:#0000000a}.dark-theme .todo-item:hover{background-color:#ffffff0a}.todo-text{flex-grow:1;margin:0 15px;transition:all .3s ease}.todo-item.completed .todo-text{text-decoration:line-through;opacity:.5}.delete-btn{background:none;border:none;font-size:1.2rem;font-weight:700;cursor:pointer;opacity:.5;transition:all .2s ease}.light-theme .delete-btn{color:#f44336}.dark-theme .delete-btn{color:#ff8a80}.todo-item:hover .delete-btn{opacity:1}.delete-btn:hover{transform:scale(1.2)}.checkbox-container{display:flex;align-items:center;cursor:pointer}.todo-checkbox{display:none}.custom-checkbox{width:22px;height:22px;border:2px solid;border-radius:50%;display:flex;justify-content:center;align-items:center;transition:all .3s ease}.light-theme .custom-checkbox{border-color:var(--accent-color-light)}.dark-theme .custom-checkbox{border-color:var(--accent-color-dark)}.todo-item.completed .custom-checkbox{background-image:var(--accent-gradient-light);border-color:transparent}.dark-theme .todo-item.completed .custom-checkbox{background-image:var(--accent-gradient-dark)}.custom-checkbox:after{content:"✓";color:#fff;font-size:14px;font-weight:700;opacity:0;transform:scale(0);transition:all .2s ease-in-out}.todo-item.completed .custom-checkbox:after{opacity:1;transform:scale(1)}.todo-list::-webkit-scrollbar{width:6px}.todo-list::-webkit-scrollbar-track{background:transparent}.todo-list::-webkit-scrollbar-thumb{border-radius:3px}.light-theme .todo-list::-webkit-scrollbar-thumb{background:#0003}.dark-theme .todo-list::-webkit-scrollbar-thumb{background:#fff3}@media(max-width:600px){.app-container{padding:0;display:block}.todo-app{width:100vw;max-width:100vw;min-height:100vh;border-radius:0;border:none;padding:40px 20px;-webkit-backdrop-filter:none;backdrop-filter:none}.todo-form{flex-direction:row}.todo-list{max-height:none}}