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

:root {
    --primary-color: #7BA5D8;
    --primary-hover: #8FB5E3;
    --secondary-color: #5A7FA0;
    --background: #1A1D24;
    --card-background: #242831;
    --text-primary: #E8EBF0;
    --text-secondary: #9BA3B4;
    --border-color: #32363F;
    --success-color: #6FCF97;
    --danger-color: #EB5757;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.4);
    --item-background: #2D3139;
    --item-hover: #363A45;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 20px;
    /* iOS safe area support */
    padding-top: max(20px, env(safe-area-inset-top));
    padding-bottom: max(20px, env(safe-area-inset-bottom));
    padding-left: max(20px, env(safe-area-inset-left));
    padding-right: max(20px, env(safe-area-inset-right));
}

.container {
    max-width: 1200px;
    margin: 0 auto;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
    flex-wrap: wrap;
    gap: 16px;
}

h1 {
    font-size: 32px;
    font-weight: 600;
    color: var(--text-primary);
}

h2 {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
}

.btn-primary {
    background-color: var(--primary-color);
    color: #1A1D24;
    border: none;
    padding: 12px 24px;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: var(--shadow);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    box-shadow: var(--shadow-hover);
}

.btn-secondary {
    background-color: var(--item-background);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    padding: 12px 24px;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-secondary:hover {
    background-color: var(--item-hover);
    border-color: var(--primary-color);
}

.lists-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
}

.list-card {
    background-color: var(--card-background);
    border-radius: 16px;
    padding: 24px;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    position: relative;
    border: 1px solid var(--border-color);
}

.list-card:hover {
    box-shadow: var(--shadow-hover);
    border-color: var(--primary-color);
}

.list-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
    gap: 8px;
}

.list-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
    flex: 1;
    cursor: pointer;
    padding: 8px;
    border-radius: 8px;
    transition: background-color 0.2s ease;
}

.list-title:hover {
    background-color: var(--item-background);
}

.list-actions {
    display: flex;
    gap: 8px;
}

.icon-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 20px;
    padding: 8px;
    border-radius: 8px;
    transition: all 0.2s ease;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
}

.icon-btn:hover {
    background-color: var(--item-background);
    color: var(--text-primary);
}

.icon-btn.delete:hover {
    background-color: rgba(235, 87, 87, 0.15);
    color: var(--danger-color);
}

.items-list {
    list-style: none;
    margin-bottom: 16px;
}

.item {
    display: flex;
    align-items: center;
    padding: 12px;
    border-radius: 10px;
    margin-bottom: 8px;
    background-color: var(--item-background);
    transition: all 0.2s ease;
    cursor: move;
    border: 1px solid transparent;
}

.item:hover {
    background-color: var(--item-hover);
    border-color: var(--border-color);
}

.item.completed .item-text {
    text-decoration: line-through;
    color: var(--text-secondary);
}

.item-checkbox {
    width: 20px;
    height: 20px;
    margin-right: 12px;
    cursor: pointer;
    accent-color: var(--primary-color);
}

.item-text {
    flex: 1;
    color: var(--text-primary);
    font-size: 15px;
    cursor: pointer;
    padding: 4px 8px;
    border-radius: 6px;
}

.item-text:hover {
    background-color: rgba(123, 165, 216, 0.1);
}

.item-delete {
    background: none;
    border: none;
    color: var(--danger-color);
    cursor: pointer;
    font-size: 18px;
    padding: 4px 8px;
    border-radius: 6px;
    transition: all 0.2s ease;
    opacity: 0.6;
}

.item-delete:hover {
    background-color: rgba(235, 87, 87, 0.15);
    opacity: 1;
}

.add-item-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--item-background);
    border: 2px dashed var(--border-color);
    border-radius: 10px;
    color: var(--text-secondary);
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.add-item-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    background-color: rgba(123, 165, 216, 0.05);
}

/* Modal Styles */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    z-index: 1000;
    animation: fadeIn 0.2s ease;
}

.modal.active {
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding-top: 10vh;
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.modal-content {
    background-color: var(--card-background);
    border-radius: 20px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
    max-width: 500px;
    width: 90%;
    animation: slideUp 0.3s ease;
    border: 1px solid var(--border-color);
}

@keyframes slideUp {
    from {
        transform: translateY(20px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 24px 24px 16px 24px;
    border-bottom: 1px solid var(--border-color);
}

.close-btn {
    background: none;
    border: none;
    font-size: 32px;
    color: var(--text-secondary);
    cursor: pointer;
    line-height: 1;
    padding: 0;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    transition: all 0.2s ease;
}

.close-btn:hover {
    background-color: var(--item-background);
    color: var(--text-primary);
}

.modal-body {
    padding: 24px;
}

.modal-body input {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    font-size: 16px;
    margin-bottom: 20px;
    transition: all 0.2s ease;
    font-family: inherit;
    color: var(--text-primary);
    background-color: var(--item-background);
}

.modal-body input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(123, 165, 216, 0.15);
    background-color: var(--card-background);
}

.modal-body input::placeholder {
    color: var(--text-secondary);
}

.modal-actions {
    display: flex;
    gap: 12px;
    justify-content: flex-end;
}

.drag-over {
    border: 2px dashed var(--primary-color);
    background-color: rgba(123, 165, 216, 0.1);
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-secondary);
    grid-column: 1 / -1;
}

.empty-state h3 {
    font-size: 24px;
    margin-bottom: 8px;
    color: var(--text-primary);
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    body {
        padding: 12px;
        padding-top: 80px;
    }

    header {
        margin-bottom: 20px;
    }

    h1 {
        font-size: 24px;
    }

    .lists-container {
        grid-template-columns: 1fr;
        gap: 16px;
    }

    .list-card {
        padding: 20px;
    }

    .modal.active {
        padding-top: 5vh;
    }

    .modal-content {
        width: 95%;
        margin: 12px;
    }

    .btn-primary, .btn-secondary {
        padding: 10px 20px;
        font-size: 15px;
    }
}

@media (max-width: 480px) {
    h1 {
        font-size: 20px;
    }

    .modal-actions {
        flex-direction: column-reverse;
    }

    .modal-actions button {
        width: 100%;
    }
}