/* Modern CSS Reset and Base Styles */
* {
    box-sizing: border-box;
}

body {
    font-family:
        "Inter",
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        Roboto,
        sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 50%, #334155 100%);
    min-height: 100vh;
    margin: 0;
    padding: 20px;
    color: #1e293b;
    line-height: 1.6;
}

/* Container with improved glass morphism effect */
.container {
    max-width: 680px;
    margin: 0 auto;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 20px;
    box-shadow:
        0 20px 40px rgba(0, 0, 0, 0.1),
        0 1px 3px rgba(0, 0, 0, 0.05);
    overflow: hidden;
    transition:
        transform 0.3s ease,
        box-shadow 0.3s ease;
}

/* Enhanced header with better typography */
h1 {
    text-align: center;
    margin: 0;
    padding: 40px 20px 30px;
    background: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 50%, #06b6d4 100%);
    color: white;
    font-size: clamp(1.8rem, 4vw, 2.5rem);
    font-weight: 700;
    letter-spacing: -0.02em;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: relative;
    overflow: hidden;
}

h1::before {
    content: "";
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(
        90deg,
        transparent,
        rgba(255, 255, 255, 0.2),
        transparent
    );
    transition: left 0.5s;
}

h1:hover::before {
    left: 100%;
}

/* Improved add item section */
.add-item {
    padding: 30px;
    display: flex;
    gap: 12px;
    background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
    border-bottom: 1px solid #e2e8f0;
}

#new-item-input {
    flex: 1;
    padding: 16px 20px;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 500;
    outline: none;
    transition: all 0.3s ease;
    background: white;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

#new-item-input:focus {
    border-color: #3b82f6;
    box-shadow:
        0 0 0 3px rgba(59, 130, 246, 0.1),
        0 4px 12px rgba(0, 0, 0, 0.1);
    transform: translateY(-1px);
}

#new-item-input::placeholder {
    color: #94a3b8;
    font-weight: 400;
}

#add-item-btn {
    padding: 16px 28px;
    background: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 100%);
    color: white;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
    position: relative;
    overflow: hidden;
}

#add-item-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(59, 130, 246, 0.4);
}

#add-item-btn:active {
    transform: translateY(0);
}

/* Modern filter buttons */
.item-filters {
    display: flex;
    padding: 25px 30px;
    gap: 8px;
    border-bottom: 1px solid #e2e8f0;
    background: white;
}

.filter-btn {
    padding: 10px 18px;
    border: 2px solid #e2e8f0;
    background: white;
    border-radius: 10px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.3s ease;
    color: #64748b;
}

.filter-btn:hover {
    background: #f1f5f9;
    border-color: #cbd5e1;
    transform: translateY(-1px);
}

.filter-btn.active {
    background: linear-gradient(135deg, #3b82f6 0%, #8b5cf6 100%);
    color: white;
    border-color: transparent;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

/* Enhanced item list */
.item-list {
    list-style: none;
    padding: 0;
    margin: 0;
    min-height: 200px;
    background: white;
}

.item-item {
    display: flex;
    align-items: center;
    padding: 20px 30px;
    border-bottom: 1px solid #f1f5f9;
    transition: all 0.3s ease;
    position: relative;
}

.item-item:hover {
    background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
}

.item-item.completed {
    opacity: 0.7;
}

.item-item.completed::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
}

/* Modern checkbox design */
.item-checkbox {
    width: 24px;
    height: 24px;
    border: 2px solid #cbd5e1;
    border-radius: 8px;
    margin-right: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: white;
}

.item-checkbox:hover {
    border-color: #3b82f6;
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.item-checkbox.completed {
    background: linear-gradient(135deg, #10b981 0%, #059669 100%);
    border-color: #10b981;
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
}

.item-checkbox.completed::after {
    content: "✓";
    color: white;
    font-size: 14px;
    font-weight: bold;
    animation: checkmark 0.3s ease;
}

@keyframes checkmark {
    0% {
        transform: scale(0) rotate(45deg);
    }
    50% {
        transform: scale(1.2) rotate(45deg);
    }
    100% {
        transform: scale(1) rotate(45deg);
    }
}

/* Enhanced item text */
.item-text {
    flex: 1;
    font-size: 16px;
    font-weight: 500;
    color: #1e293b;
    cursor: pointer;
    transition: all 0.3s ease;
    line-height: 1.5;
}

.item-text.completed {
    text-decoration: line-through;
    color: #94a3b8;
}

.item-text.editing {
    background: white;
    border: 2px solid #3b82f6;
    border-radius: 8px;
    padding: 8px 12px;
    outline: none;
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
    color: #1e293b;
    font-weight: 500;
}

/* Modern action buttons */
.item-actions {
    display: flex;
    gap: 8px;
    opacity: 0;
    transition: all 0.3s ease;
    transform: translateX(10px);
}

.item-item:hover .item-actions {
    opacity: 1;
    transform: translateX(0);
}

.item-btn {
    padding: 8px 14px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 12px;
    font-weight: 600;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.edit-btn {
    background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
    color: white;
    box-shadow: 0 2px 8px rgba(245, 158, 11, 0.3);
}

.edit-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(245, 158, 11, 0.4);
}

.edit-btn svg {
    width: 18px;
}

.delete-btn {
    background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
    color: white;
    box-shadow: 0 2px 8px rgba(239, 68, 68, 0.3);
}

.delete-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(239, 68, 68, 0.4);
}

.delete-btn svg {
    width: 18px;
}

/* Enhanced error message */
.error-message {
    background: linear-gradient(135deg, #fef2f2 0%, #fee2e2 100%);
    color: #991b1b;
    padding: 16px 30px;
    margin: 20px 30px;
    border: 1px solid #fecaca;
    border-left: 4px solid #ef4444;
    border-radius: 12px;
    font-size: 14px;
    font-weight: 500;
    box-shadow: 0 2px 8px rgba(239, 68, 68, 0.1);
}

/* Beautiful empty state */
.empty-state {
    text-align: center;
    padding: 80px 20px;
    color: #64748b;
    font-size: 16px;
    font-weight: 500;
}

.empty-state::before {
    content: "✨";
    display: block;
    font-size: 64px;
    margin-bottom: 20px;
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%,
    100% {
        transform: translateY(0px);
    }
    50% {
        transform: translateY(-10px);
    }
}

/* Enhanced mobile responsiveness */
@media (max-width: 768px) {
    body {
        padding: 10px;
    }

    .container {
        margin: 0;
        border-radius: 16px;
        min-height: calc(100vh - 20px);
    }

    h1 {
        padding: 30px 20px 25px;
        font-size: 1.8rem;
    }

    .add-item {
        flex-direction: column;
        padding: 25px 20px;
        gap: 16px;
    }

    #new-item-input,
    #add-item-btn {
        width: 100%;
    }

    .item-filters {
        justify-content: center;
        flex-wrap: wrap;
        padding: 20px;
    }

    .item-item {
        padding: 16px 20px;
    }

    .item-actions {
        opacity: 1;
        transform: translateX(0);
    }

    .empty-state {
        padding: 60px 20px;
    }

    .empty-state::before {
        font-size: 48px;
    }
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    .container {
        background: rgba(30, 41, 59, 0.95);
        border-color: rgba(255, 255, 255, 0.1);
    }

    .add-item {
        background: linear-gradient(135deg, #1e293b 0%, #334155 100%);
        border-color: #475569;
    }

    #new-item-input {
        background: #334155;
        border-color: #475569;
        color: #f1f5f9;
    }

    #new-item-input::placeholder {
        color: #64748b;
    }

    .item-filters {
        background: #1e293b;
        border-color: #475569;
    }

    .filter-btn {
        background: #334155;
        border-color: #475569;
        color: #cbd5e1;
    }

    .filter-btn:hover {
        background: #475569;
    }

    .item-list {
        background: #1e293b;
    }

    .item-item {
        border-color: #334155;
    }

    .item-item:hover {
        background: linear-gradient(135deg, #334155 0%, #475569 100%);
    }

    .item-text {
        color: #f1f5f9;
    }

    .item-checkbox {
        background: #334155;
        border-color: #475569;
    }

    .empty-state {
        color: #94a3b8;
    }

    .item-text.editing {
        background: #334155;
        border-color: #60a5fa;
        color: #f1f5f9;
        box-shadow: 0 0 0 3px rgba(96, 165, 250, 0.1);
    }
}

/* Smooth scrolling and focus improvements */
html {
    scroll-behavior: smooth;
}

*:focus {
    outline: 2px solid #3b82f6;
    outline-offset: 2px;
}

/* Loading animation for dynamic content */
@keyframes shimmer {
    0% {
        background-position: -200px 0;
    }
    100% {
        background-position: calc(200px + 100%) 0;
    }
}

.loading {
    background: linear-gradient(90deg, #f1f5f9 25%, #e2e8f0 50%, #f1f5f9 75%);
    background-size: 200px 100%;
    animation: shimmer 1.5s infinite;
}