:root {
    --background: #1E1F28;
    --primary-color: #2E2F3E;
    --secondary-color: #525466;
    --accent-color: #FF6B6B;
    --text-color: #EAEAEA;
    --input-background: #3A3B4E;
    --button-background: #FF6B6B;
    --button-text: #FFFFFF;
    --checkbox-border: #FF6B6B;
    --checkbox-background: #FF6B6B;
    --checkbox-tick: #2E2F3E;
    --delete-hover: #FF3B3B;
}

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

html {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    font-size: 16px;
    color: var(--text-color);
}

body {
    min-height: 100vh;
    padding: 20px;
    background-color: var(--background);
    display: flex;
    flex-direction: column;
    align-items: center;
}

h1 {
    margin-top: 60px;
    margin-bottom: 20px;
    font-size: 3rem;
    font-weight: 700;
    text-align: center;
    color: var(--accent-color);
}

.wrapper {
    width: 700px;
    max-width: 100%;
    display: flex;
    flex-direction: column;
    gap: 20px;
    padding: 20px;
    background-color: var(--primary-color);
    border-radius: 15px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.5);
}

form {
    display: flex;
    align-items: center;
    position: relative;
}

#todo-input {
    flex-grow: 1;
    padding: 15px 20px;
    background: var(--input-background);
    border: none;
    border-radius: 30px;
    font-size: 1rem;
    color: var(--text-color);
    margin-right: 10px;
}

#todo-input:focus {
    outline: none;
}

#add-button {
    padding: 15px 20px;
    background-color: var(--button-background);
    border: none;
    border-radius: 30px;
    font-size: 1rem;
    color: var(--button-text);
    cursor: pointer;
    transition: background-color 0.3s ease;
}

#add-button:hover {
    background-color: var(--delete-hover);
}

#todo-list {
    list-style: none;
    margin-top: 20px;
}

.todo {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 15px;
    background-color: var(--primary-color);
    border-radius: 15px;
    margin-bottom: 10px;
    transition: background-color 0.3s ease;
}

.todo:hover {
    background-color: var(--input-background);
}

.todo-text {
    flex-grow: 1;
    margin-left: 10px;
    transition: color 0.3s ease, text-decoration 0.3s ease;
}

.custom-checkbox {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 24px;
    height: 24px;
    border: 2px solid var(--checkbox-border);
    border-radius: 50%;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

input[type="checkbox"] {
    display: none;
}

input[type="checkbox"]:checked ~ .custom-checkbox {
    background-color: var(--checkbox-background);
}

input[type="checkbox"]:checked ~ .custom-checkbox svg {
    fill: var(--checkbox-tick);
}

input[type="checkbox"]:checked ~ .todo-text {
    text-decoration: line-through;
    color: var(--secondary-color);
}

.delete-button {
    background: none;
    border: none;
    cursor: pointer;
    transition: fill 0.3s ease;
}

.delete-button svg {
    fill: var(--secondary-color);
}

.delete-button:hover svg {
    fill: var(--delete-hover);
}

@media (max-width: 600px) {
    form {
        flex-direction: column;
        align-items: stretch;
    }

    #add-button {
        width: 100%;
        margin-top: 10px;
    }
}