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

:root {
    --bg-color: #f4f6f8;
    --card-color: #ffffff;
    --primary-color: #4f46e5;
    --primary-hover: #4338ca;
    --text-color: #1f2937;
    --secondary-text: #6b7280;
    --border-color: #e5e7eb;
    --danger-color: #ef4444;
    --success-color: #10b981;
}

body {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: var(--bg-color);
    font-family: "Inter", "Segoe UI", sans-serif;
    color: var(--text-color);
}


/* App Container */

.todo-app {
    width: 100%;
    max-width: 520px;
    background: var(--card-color);
    padding: 32px;
    border-radius: 20px;
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.08);
}


/* Title */

.todo-app h1 {
    text-align: center;
    margin-bottom: 28px;
    font-size: 32px;
    font-weight: 700;
}


/* Input Section */

.todo-form {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
}

.todo-form input {
    flex: 1;
    padding: 14px 16px;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    outline: none;
    font-size: 15px;
    transition: 0.2s;
}

.todo-form input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.15);
}


button {
    border: none;
    cursor: pointer;
    font-size: 14px;
    font-weight: 600;
    border-radius: 10px;
    transition: 0.2s;
}


/* Add Button */

#addBtn {
    padding: 0 22px;
    background: var(--primary-color);
    color: white;
}

#addBtn:hover {
    background: var(--primary-hover);
}


/* Filters */

.filters {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 24px;
}

.filter,
.sort {
    display: flex;
    gap: 8px;
}

.filter button,
.sort button {
    padding: 8px 12px;
    background: #f9fafb;
    color: var(--secondary-text);
    border: 1px solid var(--border-color);
}


.filter button:hover,
.sort button:hover {
    color: var(--primary-color);
}


/* Active Buttons */

.activeFilterBtn,
.activeSortBtn {
    background: var(--primary-color) !important;
    color: white !important;
    border-color: var(--primary-color) !important;
}


/* Todo List */

#todoList {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 12px;
    max-height: 30vh;
    overflow-y: auto;
}


#todoList li {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    border: 1px solid var(--border-color);
    border-radius: 14px;
    background: #fff;
    transition: 0.2s;
}


#todoList li:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.06);
}


#todoList span {
    flex: 1;
    font-size: 15px;
}


/* Checkbox */

#todoList input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
}


/* Delete Button */

#todoList button {
    padding: 8px 12px;
    background: #fee2e2;
    color: var(--danger-color);
}


#todoList button:hover {
    background: var(--danger-color);
    color: white;
}


/* Footer */

.todo-footer {
    margin-top: 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}


#itemsLeft {
    color: var(--secondary-text);
    font-size: 14px;
}


#clearCompletedBtn {
    padding: 10px 14px;
    background: #f3f4f6;
    color: var(--text-color);
}


#clearCompletedBtn:hover {
    background: #e5e7eb;
}


/* Responsive */

@media (max-width: 550px) {

    .todo-app {
        margin: 20px;
        padding: 24px;
    }


    .filters {
        flex-direction: column;
    }


    .filter,
    .sort {
        justify-content: center;
    }


    .todo-form {
        flex-direction: column;
    }


    #addBtn {
        height: 45px;
    }
}