:root {
            --bg-color: #1a1a2e;
            --container-color: #16213e;
            --primary-color: #0f3460;
            --accent-color: #e94560;
            --text-color: #e4e4e4;
            --text-muted-color: #a0a0a0;
            --completed-color: #535e88;
            --shadow-color: rgba(22, 33, 62, 0.4);
            --font-family: 'Poppins', sans-serif;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: var(--font-family);
            background-color: var(--bg-color);
            color: var(--text-color);
            display: flex;
            justify-content: center;
            align-items: flex-start;
            min-height: 100vh;
            padding-top: 50px;
        }

        /* ------------------- */
        /*   Main App Layout   */
        /* ------------------- */
        .app-container {
            width: 100%;
            max-width: 550px;
            background: var(--container-color);
            padding: 2rem;
            border-radius: 1.5rem;
            box-shadow: 0 15px 40px var(--shadow-color);
            margin: 0 15px;
        }

        header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 1.5rem;
            border-bottom: 2px solid var(--primary-color);
            padding-bottom: 1rem;
        }

        header h1 {
            font-weight: 600;
            font-size: 2rem;
            color: var(--text-color);
        }

        header #date {
            font-size: 1rem;
            color: var(--text-muted-color);
            font-weight: 300;
        }

        /* ------------------- */
        /*   New Task Form     */
        /* ------------------- */
        #new-task-form {
            display: flex;
            gap: 0.5rem;
            margin-bottom: 2rem;
        }

        #new-task-input {
            flex: 1;
            padding: 0.8rem 1rem;
            background-color: var(--primary-color);
            border: none;
            border-radius: 0.5rem;
            color: var(--text-color);
            font-size: 1rem;
            font-family: var(--font-family);
            outline: none;
            transition: all 0.3s ease;
        }

        #new-task-input::placeholder {
            color: var(--text-muted-color);
        }
        
        #new-task-input:focus {
            box-shadow: 0 0 0 3px var(--accent-color), 0 0 15px var(--accent-color);
        }

        #new-task-submit {
            padding: 0.8rem 1.2rem;
            font-size: 1rem;
            font-weight: 600;
            background-color: var(--accent-color);
            color: #fff;
            border: none;
            border-radius: 0.5rem;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        #new-task-submit:hover {
            opacity: 0.85;
            transform: translateY(-2px);
        }

        #new-task-submit:active {
            transform: translateY(0);
            opacity: 1;
        }

        /* ------------------- */
        /*    Task List & Items */
        /* ------------------- */
        #task-list-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 1rem;
        }

        #task-list-header h2 {
            font-size: 1.5rem;
            font-weight: 500;
        }

        #task-filters button {
            background: none;
            border: none;
            color: var(--text-muted-color);
            font-family: var(--font-family);
            font-size: 0.9rem;
            margin-left: 1rem;
            cursor: pointer;
            transition: color 0.3s ease;
        }

        #task-filters button:hover {
            color: var(--accent-color);
        }
        
        #task-filters button.active {
            color: var(--accent-color);
            font-weight: 600;
        }

        #tasks {
            display: flex;
            flex-direction: column;
            gap: 0.75rem;
        }

        .task {
            display: flex;
            align-items: center;
            background-color: var(--primary-color);
            padding: 1rem;
            border-radius: 0.5rem;
            transition: all 0.3s ease;
            user-select: none;
        }

        .task:hover {
            transform: scale(1.02);
            box-shadow: 0 5px 15px rgba(0,0,0,0.2);
        }
        
        .task .checkbox {
            -webkit-appearance: none;
            appearance: none;
            background-color: transparent;
            margin-right: 1rem;
            font: inherit;
            color: var(--text-muted-color);
            width: 1.5em;
            height: 1.5em;
            border: 0.15em solid var(--text-muted-color);
            border-radius: 50%;
            transform: translateY(-0.075em);
            display: grid;
            place-content: center;
            cursor: pointer;
            transition: all 0.2s ease;
        }

        .task .checkbox::before {
            content: "";
            width: 0.65em;
            height: 0.65em;
            border-radius: 50%;
            transform: scale(0);
            transition: 120ms transform ease-in-out;
            box-shadow: inset 1em 1em var(--accent-color);
        }

        .task .checkbox:checked {
            border-color: var(--accent-color);
        }

        .task .checkbox:checked::before {
            transform: scale(1);
        }
        
        .task .content {
            flex: 1;
            font-size: 1rem;
            transition: all 0.3s ease;
        }

        .task.completed .content {
            color: var(--completed-color);
            text-decoration: line-through;
        }

        .task .actions button {
            background: none;
            border: none;
            color: var(--text-muted-color);
            font-size: 1.2rem;
            cursor: pointer;
            transition: all 0.3s ease;
            opacity: 0;
            visibility: hidden;
            transform: scale(0.8);
        }
        
        .task:hover .actions button {
            opacity: 1;
            visibility: visible;
            transform: scale(1);
        }
        
        .task .actions .delete:hover {
            color: #ff3b3b;
        }

        /* ------------------- */
        /*   Footer/Summary    */
        /* ------------------- */
        #task-summary {
            margin-top: 2rem;
            padding-top: 1rem;
            border-top: 2px solid var(--primary-color);
            color: var(--text-muted-color);
            text-align: center;
            font-size: 0.9rem;
        }

        /* ------------------- */
        /*    Responsiveness   */
        /* ------------------- */
        @media (max-width: 600px) {
            body {
                padding-top: 20px;
            }
            .app-container {
                padding: 1.5rem;
                border-radius: 1rem;
            }
            header {
                flex-direction: column;
                align-items: flex-start;
                gap: 0.5rem;
            }
            #task-list-header {
                flex-direction: column;
                align-items: flex-start;
                gap: 0.75rem;
            }
            #task-filters button {
                margin-left: 0;
                margin-right: 1rem;
            }
        }