/* CSS Custom Properties for better maintainability */
:root {
    --primary-bg: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    --card-bg: rgba(255, 255, 255, 0.1);
    --card-border: rgba(255, 255, 255, 0.2);
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.8);
    --text-muted: rgba(255, 255, 255, 0.6);
    --positive-color: #4caf50;
    --negative-color: #f44336;
    --neutral-color: #9e9e9e;
    --warning-color: #ff9800;
    --accent-gradient: linear-gradient(45deg, #f7931e, #ffeb3b, #4caf50, #2196f3);
    --border-radius: 12px;
    --box-shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --container-max-width: 1200px;
    --grid-gap: 20px;
}

/* Reset and base styles */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background: var(--primary-bg);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-primary);
    line-height: 1.6;
}

/* Container and layout */
.container {
    max-width: var(--container-max-width);
    margin: 0 auto;
    padding-top: 20px;
}

/* Header styles */
.header {
    text-align: center;
    margin-bottom: 40px;
}

.header h1 {
    font-size: clamp(2rem, 5vw, 3rem);
    font-weight: 700;
    margin-bottom: 8px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: shimmer 3s ease-in-out infinite;
}

@keyframes shimmer {
    0%, 100% { filter: hue-rotate(0deg); }
    50% { filter: hue-rotate(90deg); }
}

.header p {
    font-size: 1.2rem;
    color: var(--text-secondary);
}

/* Controls section */
.controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    gap: var(--grid-gap);
    flex-wrap: wrap;
}

.search-container {
    position: relative;
    flex: 1;
    max-width: 400px;
}

.search-input {
    width: 100%;
    padding: 12px 20px 12px 50px;
    font-size: 1rem;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    backdrop-filter: blur(10px);
    transition: var(--transition);
}

.search-input:focus {
    outline: none;
    border-color: var(--positive-color);
    box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.1);
}

.search-input::placeholder {
    color: var(--text-muted);
}

.search-icon {
    position: absolute;
    left: 15px;
    top: 50%;
    transform: translateY(-50%);
    width: 20px;
    height: 20px;
    color: var(--text-muted);
    pointer-events: none;
}

.refresh-btn {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    backdrop-filter: blur(10px);
    transition: var(--transition);
    white-space: nowrap;
}

.refresh-btn:hover:not(:disabled) {
    background: rgba(255, 255, 255, 0.15);
    transform: translateY(-2px);
    box-shadow: var(--box-shadow);
}

.refresh-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.refresh-btn.loading .refresh-icon {
    animation: spin 1s linear infinite;
}

@keyframes spin {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.refresh-icon {
    width: 20px;
    height: 20px;
    transition: var(--transition);
}

/* Last updated timestamp */
.last-updated {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 20px;
}

/* Request status display */
.request-status {
    text-align: center;
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-bottom: 15px;
    padding: 8px 16px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--border-radius);
    backdrop-filter: blur(10px);
}

.request-status.warning {
    color: var(--warning-color);
    border-color: rgba(255, 152, 0, 0.3);
    background: rgba(255, 152, 0, 0.1);
}

.request-status.error {
    color: var(--negative-color);
    border-color: rgba(244, 67, 54, 0.3);
    background: rgba(244, 67, 54, 0.1);
}

/* Crypto grid */
.crypto-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--grid-gap);
    margin-bottom: 40px;
}

/* Crypto card */
.crypto-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--border-radius);
    padding: 24px;
    backdrop-filter: blur(10px);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.crypto-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--box-shadow);
    border-color: rgba(255, 255, 255, 0.3);
}

.crypto-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--accent-gradient);
    opacity: 0;
    transition: var(--transition);
}

.crypto-card:hover::before {
    opacity: 1;
}

/* Crypto header */
.crypto-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 16px;
}

.crypto-info {
    display: flex;
    align-items: center;
    gap: 12px;
}

.crypto-icon {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    object-fit: cover;
}

.crypto-name {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 2px;
}

.crypto-symbol {
    font-size: 0.9rem;
    color: var(--text-muted);
    text-transform: uppercase;
}

.crypto-rank {
    font-size: 0.9rem;
    color: var(--text-muted);
    background: rgba(255, 255, 255, 0.1);
    padding: 4px 8px;
    border-radius: 6px;
}

/* Price section */
.crypto-price {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.market-cap {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 16px;
}

/* Change indicators */
.crypto-changes {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
}

.change-item {
    text-align: center;
    padding: 8px;
    background: rgba(255, 255, 255, 0.05);
    border-radius: 6px;
    transition: var(--transition);
}

.change-item:hover {
    background: rgba(255, 255, 255, 0.1);
}

.change-label {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-bottom: 4px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.change-value {
    font-size: 0.9rem;
    font-weight: 600;
}

.change-value.positive {
    color: var(--positive-color);
}

.change-value.negative {
    color: var(--negative-color);
}

.change-value.neutral {
    color: var(--neutral-color);
}

/* Loading state */
.loading-grid {
    display: none;
    text-align: center;
    padding: 60px 20px;
    color: var(--text-muted);
}

.loading-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid rgba(255, 255, 255, 0.2);
    border-top: 3px solid var(--positive-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

/* Error state */
.error {
    background: rgba(244, 67, 54, 0.1);
    border: 1px solid rgba(244, 67, 54, 0.3);
    border-radius: var(--border-radius);
    padding: 20px;
    text-align: center;
    color: var(--negative-color);
    display: none;
    margin: 20px 0;
}

.error.show {
    display: block;
    animation: fadeIn 0.5s ease;
}

.error h3 {
    margin-bottom: 8px;
    font-size: 1.2rem;
}

/* Empty state */
.empty-state {
    text-align: center;
    color: var(--text-muted);
    padding: 60px 20px;
    font-size: 1.1rem;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--border-radius);
    backdrop-filter: blur(10px);
}

/* Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Responsive design */
@media (max-width: 768px) {
    body {
        padding: 15px;
    }

    .header h1 {
        font-size: 2.2rem;
    }

    .controls {
        flex-direction: column;
        align-items: stretch;
        gap: 15px;
    }

    .search-container {
        max-width: none;
    }

    .crypto-grid {
        grid-template-columns: 1fr;
        gap: 15px;
    }

    .crypto-card {
        padding: 20px;
    }

    .crypto-changes {
        grid-template-columns: repeat(2, 1fr);
        gap: 8px;
    }
}

@media (max-width: 480px) {
    .crypto-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .crypto-rank {
        align-self: flex-end;
    }

    .crypto-changes {
        grid-template-columns: 1fr;
    }
}

/* Performance optimizations */
.crypto-icon {
    will-change: transform;
}

.crypto-card {
    contain: layout;
}

/* Accessibility improvements */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus indicators for keyboard navigation */
.search-input:focus,
.refresh-btn:focus {
    outline: 2px solid var(--positive-color);
    outline-offset: 2px;
}