/* ===== CSS Reset & Base Styles ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-bg: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --panel-bg: rgba(255, 255, 255, 0.95);
    --border-color: rgba(222, 226, 230, 0.3);
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --accent-color: #667eea;
    --accent-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --error-color: #e74c3c;
    --success-color: #27ae60;
    --focus-outline: 2px solid #667eea;
    --shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.12);
    --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.15);
    --border-radius: 12px;
    --header-bg: rgba(255, 255, 255, 0.98);
    --footer-bg: rgba(255, 255, 255, 0.98);
}

[data-theme="dark"] {
    --primary-bg: linear-gradient(135deg, #1a1a2e 0%, #16213e 100%);
    --panel-bg: rgba(30, 30, 46, 0.95);
    --border-color: rgba(255, 255, 255, 0.1);
    --text-primary: #e0e0e0;
    --text-secondary: #a0a0a0;
    --accent-color: #8b9aff;
    --accent-gradient: linear-gradient(135deg, #8b9aff 0%, #a78bfa 100%);
    --error-color: #ff6b6b;
    --success-color: #51cf66;
    --focus-outline: 2px solid #8b9aff;
    --shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 12px 40px rgba(0, 0, 0, 0.5);
    --header-bg: rgba(20, 20, 30, 0.98);
    --footer-bg: rgba(20, 20, 30, 0.98);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--primary-bg);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    transition: background 0.3s ease, color 0.3s ease;
}

/* ===== Header ===== */
header {
    background: var(--header-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    padding: 1.5rem 2rem;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1600px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.theme-toggle {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: none;
    background: var(--accent-gradient);
    color: white;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    box-shadow: var(--shadow-md);
}

.theme-toggle:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-lg);
}

.theme-toggle:active {
    transform: scale(0.95);
}

.theme-toggle .sun-icon {
    display: block;
    font-size: 24px;
    line-height: 1;
}

.theme-toggle .moon-icon {
    display: none;
    font-size: 24px;
    line-height: 1;
}

[data-theme="dark"] .theme-toggle .sun-icon {
    display: none;
}

[data-theme="dark"] .theme-toggle .moon-icon {
    display: block;
}

/* ===== Main Container ===== */
main.app-container {
    flex: 1;
    display: grid;
    gap: 1.5rem;
    padding: 2rem;
    max-width: 1600px;
    margin: 0 auto;
    width: 100%;
}

/* Desktop Layout: 3 columns side by side at >= 1024px */
@media (min-width: 1024px) {
    main.app-container {
        grid-template-columns: repeat(3, 1fr);
        align-items: start;
    }
}

/* Tablet/Mobile Layout: stacked vertically below 1024px */
@media (max-width: 1023px) {
    main.app-container {
        grid-template-columns: 1fr;
    }
}

/* ===== Panel Styles ===== */
.panel {
    background: var(--panel-bg);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: var(--shadow-md);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.panel:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.panel h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.panel h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

.section {
    margin-bottom: 2rem;
}

.section:last-child {
    margin-bottom: 0;
}

/* ===== Predefined Palette Grid ===== */
.palette-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(45px, 1fr));
    gap: 0.5rem;
}

.palette-swatch {
    width: 100%;
    height: 45px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: transform 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
    position: relative;
}

.palette-swatch:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-md);
}

.palette-swatch:focus {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

.palette-swatch.selected {
    border-color: var(--accent-color);
    border-width: 3px;
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.2);
}

/* ===== Interactive Color Picker ===== */
.color-picker-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.picker-controls {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.picker-controls label {
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Hue Slider */
.hue-slider-container {
    position: relative;
    height: 30px;
}

.hue-gradient {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(to right, 
        #ff0000 0%, 
        #ffff00 16.67%, 
        #00ff00 33.33%, 
        #00ffff 50%, 
        #0000ff 66.67%, 
        #ff00ff 83.33%, 
        #ff0000 100%);
    border-radius: var(--border-radius);
    pointer-events: none;
}

#hueSlider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 30px;
    background: transparent;
    cursor: pointer;
    position: relative;
    z-index: 1;
}

#hueSlider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 30px;
    background: #ffffff;
    border: 2px solid var(--text-primary);
    border-radius: 3px;
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

#hueSlider::-moz-range-thumb {
    width: 20px;
    height: 30px;
    background: #ffffff;
    border: 2px solid var(--text-primary);
    border-radius: 3px;
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

#hueSlider:focus {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

/* Saturation/Lightness Canvas */
#slCanvas {
    width: 100%;
    max-width: 280px;
    height: 200px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: crosshair;
    display: block;
    touch-action: none;
}

#slCanvas:focus {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

.sl-indicator {
    position: absolute;
    width: 16px;
    height: 16px;
    border: 2px solid #ffffff;
    border-radius: 50%;
    pointer-events: none;
    box-shadow: 0 0 3px rgba(0, 0, 0, 0.5);
    transform: translate(-50%, -50%);
    z-index: 10;
}

/* ===== Manual Input ===== */
.manual-input {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.input-group label {
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.input-group input[type="text"],
.input-group input[type="number"] {
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-family: 'Courier New', monospace;
    transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.input-group input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.input-group input.invalid {
    border-color: var(--error-color);
}

.rgb-inputs {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.5rem;
}

.rgb-inputs input {
    text-align: center;
}

.error-message {
    font-size: 0.75rem;
    color: var(--error-color);
    min-height: 1rem;
    display: block;
}

/* ===== Text Preview Panel ===== */
.comparison-panel label {
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    display: block;
}

.comparison-panel input[type="text"] {
    width: 100%;
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    margin-bottom: 1rem;
    transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.comparison-panel input[type="text"]:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
}

.preview-area {
    background: 
        linear-gradient(45deg, #e9ecef 25%, transparent 25%),
        linear-gradient(-45deg, #e9ecef 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, #e9ecef 75%),
        linear-gradient(-45deg, transparent 75%, #e9ecef 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
    background-color: #ffffff;
    padding: 2rem;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    min-height: 150px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: 600;
    text-align: center;
    word-wrap: break-word;
    overflow-wrap: break-word;
}

/* ===== Current Color Swatch ===== */
.current-color-swatch {
    width: 100%;
    height: 150px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    background: 
        linear-gradient(45deg, #e9ecef 25%, transparent 25%),
        linear-gradient(-45deg, #e9ecef 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, #e9ecef 75%),
        linear-gradient(-45deg, transparent 75%, #e9ecef 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
}

.current-color-swatch::after {
    content: '';
    display: block;
    width: 100%;
    height: 100%;
    border-radius: 4px;
}

/* ===== Color Output ===== */
.color-output {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.output-row {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.output-row label {
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.output-value-container {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    position: relative;
}

.output-value {
    flex: 1;
    padding: 0.5rem 0.75rem;
    background-color: var(--primary-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-family: 'Courier New', monospace;
    font-size: 0.9375rem;
}

.copy-btn {
    padding: 0.5rem;
    background: var(--accent-gradient);
    color: #ffffff;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.15s ease, box-shadow 0.15s ease;
    box-shadow: var(--shadow-sm);
}

.copy-btn:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-md);
}

.copy-btn:focus {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

.copy-btn:active {
    transform: scale(0.95);
}

.copy-feedback {
    position: absolute;
    right: 0;
    top: -1.5rem;
    background-color: var(--success-color);
    color: #ffffff;
    padding: 0.25rem 0.5rem;
    border-radius: var(--border-radius);
    font-size: 0.75rem;
    font-weight: 500;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
    white-space: nowrap;
}

.copy-feedback.show {
    opacity: 1;
}

/* ===== Pin Button ===== */
.pin-btn {
    width: 100%;
    padding: 0.75rem;
    background: var(--accent-gradient);
    color: #ffffff;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: transform 0.15s ease, box-shadow 0.15s ease;
    box-shadow: var(--shadow-sm);
}

.pin-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.pin-btn:focus {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

.pin-btn:active {
    transform: translateY(0);
}

/* ===== Pinned Colors ===== */
.pinned-count {
    font-weight: 400;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.pinned-colors-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(50px, 1fr));
    gap: 0.5rem;
    min-height: 60px;
}

.pinned-colors-grid.empty {
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-style: italic;
}

.pinned-swatch {
    width: 100%;
    height: 50px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: transform 0.15s ease, box-shadow 0.15s ease;
    position: relative;
}

.pinned-swatch:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-md);
}

.pinned-swatch:focus {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

.pinned-hint {
    margin-top: 0.75rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
    font-style: italic;
}

/* ===== Footer ===== */
footer {
    background: var(--footer-bg);
    backdrop-filter: blur(10px);
    border-top: 1px solid var(--border-color);
    padding: 1rem 2rem;
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* ===== Accessibility & Focus Styles ===== */
button:focus-visible,
input:focus-visible,
.palette-swatch:focus-visible,
.pinned-swatch:focus-visible {
    outline: var(--focus-outline);
    outline-offset: 2px;
}

/* Remove default focus for mouse users */
button:focus:not(:focus-visible),
input:focus:not(:focus-visible) {
    outline: none;
}

/* ===== Responsive Adjustments ===== */
@media (max-width: 768px) {
    header {
        padding: 1rem 1.5rem;
    }

    header h1 {
        font-size: 1.5rem;
    }

    main.app-container {
        padding: 1rem;
        gap: 1rem;
    }

    .panel {
        padding: 1rem;
    }

    .panel h2 {
        font-size: 1.25rem;
        margin-bottom: 1rem;
    }

    .preview-area {
        font-size: 1.5rem;
        padding: 1.5rem;
        min-height: 120px;
    }

    .current-color-swatch {
        height: 120px;
    }

    #slCanvas {
        max-width: 100%;
        height: 180px;
    }
}

@media (max-width: 480px) {
    .palette-grid {
        grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
        gap: 0.375rem;
    }

    .palette-swatch {
        height: 40px;
    }

    .pinned-colors-grid {
        grid-template-columns: repeat(auto-fill, minmax(45px, 1fr));
    }

    .pinned-swatch {
        height: 45px;
    }
}