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

/* colors and sizes */
:root {
    --primary: #3498db;
    --secondary: #2ecc71;
    --danger: #e74c3c;
    --dark: #333;
    --light: #fff;
    --gray: #bdc3c7;
    --spacing: 1rem;
    --radius: 8px;
}

/* page settings */
html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--dark);
    background-color: #ecf0f1;
    min-height: 100vh;
    transition: background-color 0.5s ease;
}

/* main layout */
.page-container {
    width: 100%;
    min-height: 100vh;
    display: grid;
    grid-template-rows: auto 1fr auto;
    background-color: #ecf0f1;
    transition: background-color 0.5s ease;
}

/* top header */
.page-header {
    text-align: center;
    padding: 2rem 1rem;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: var(--light);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.page-header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.subtitle {
    font-size: 1rem;
    font-weight: 300;
    opacity: 0.9;
}

/* center content */
.content-wrapper {
    max-width: 600px;
    margin: 0 auto;
    padding: 2rem 1rem;
    width: 100%;
}

/* card styling */
section {
    margin-bottom: 1.5rem;
    background: var(--light);
    padding: 1.5rem;
    border-radius: var(--radius);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    animation: slideIn 0.6s ease-out backwards;
}

/* animation for sections */
section:nth-child(2) { animation-delay: 0s; }
section:nth-child(3) { animation-delay: 0.1s; }
section:nth-child(4) { animation-delay: 0.2s; }
section:nth-child(5) { animation-delay: 0.3s; }

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

/* titles in sections */
.section-title {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--primary);
}

/* input field styling */
.input-label {
    display: block;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.color-input {
    width: 100%;
    padding: 1rem;
    font-size: 1.2rem;
    border: 2px solid var(--gray);
    border-radius: var(--radius);
    font-family: 'Courier New', monospace;
    letter-spacing: 2px;
    text-align: center;
    transition: all 0.3s ease;
    cursor: text;
}

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

.color-input:hover:not(:focus) {
    border-color: #95a5a6;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

/* good input */
.color-input.valid {
    border-color: var(--secondary);
    box-shadow: 0 0 0 3px rgba(46, 204, 113, 0.15);
}

/* bad input */
.color-input.invalid {
    border-color: var(--danger);
    animation: shake 0.3s ease;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}

.input-hint {
    font-size: 0.9rem;
    color: #7f8c8d;
    margin-top: 0.5rem;
    font-style: italic;
}

/* error message */
.error-message {
    color: var(--danger);
    font-size: 0.9rem;
    font-weight: 500;
    margin-top: 1rem;
    padding: 1rem;
    background-color: rgba(231, 76, 60, 0.1);
    border-left: 3px solid var(--danger);
    border-radius: 3px;
    display: block;
    transition: opacity 0.2s ease;
}

.error-message.hidden {
    display: none;
}

/* display boxes */
.display-area, .hex-area, .rgb-area, 
.color-name-area, .brightness-area, .preview-area {
    padding: 1.5rem;
    background-color: rgba(52, 152, 219, 0.05);
    border-radius: var(--radius);
    border: 1px solid rgba(52, 152, 219, 0.2);
    margin-bottom: 1.5rem;
}

.display-area:last-child, .hex-area:last-child, .rgb-area:last-child,
.color-name-area:last-child, .brightness-area:last-child, .preview-area:last-child {
    margin-bottom: 0;
}

/* text labels */
.display-label {
    font-size: 0.85rem;
    font-weight: 700;
    color: #7f8c8d;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 0.5rem;
}

/* color displays */
.color-display, .hex-display, .rgb-display, .color-name-display {
    font-family: 'Courier New', monospace;
    font-weight: bold;
    color: var(--primary);
    text-align: center;
    transition: all 0.4s ease;
    word-break: break-all;
}

.color-display {
    font-size: 3rem;
    min-height: 5rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.hex-display, .rgb-display, .color-name-display {
    font-size: 1.1rem;
}

/* clickable hex */
.hex-display {
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 4px;
    transition: all 0.2s ease;
}

.hex-display:hover {
    background-color: rgba(52, 152, 219, 0.1);
    transform: scale(1.05);
}

/* brightness bar */
.brightness-container {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.brightness-bar {
    flex: 1;
    height: 20px;
    background: linear-gradient(to right, #000, #fff);
    border-radius: 4px;
    border: 1px solid var(--gray);
    position: relative;
}

.brightness-percent {
    min-width: 50px;
    text-align: right;
    font-weight: 600;
    color: var(--primary);
}

/* color preview box */
.color-swatch {
    width: 100%;
    height: 100px;
    border-radius: var(--radius);
    border: 2px solid var(--gray);
    background-color: #000;
    transition: background-color 0.4s ease;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

/* buttons layout */
.button-section {
    margin-top: 2rem;
}

.button-group {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
}

/* button styling */
.btn {
    padding: 1rem;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    width: 100%;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
}

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

/* button colors */
.reset-btn {
    background-color: var(--danger);
    color: var(--light);
}

.reset-btn:hover { background-color: #c0392b; }

.random-btn {
    background-color: var(--secondary);
    color: var(--light);
}

.random-btn:hover { background-color: #27ae60; }

.copy-btn {
    background-color: var(--primary);
    color: var(--light);
}

.copy-btn:hover { background-color: #2980b9; }

/* history grid */
.color-history {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 1rem;
}

/* history item styling */
.history-item {
    width: 100%;
    aspect-ratio: 1;
    border-radius: var(--radius);
    border: 2px solid var(--gray);
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--light);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
}

.history-item:hover {
    transform: scale(1.1);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

/* empty slots */
.history-item.empty {
    background-color: #ecf0f1;
    color: #7f8c8d;
    cursor: not-allowed;
}

/* clear button */
.clear-history-btn {
    background-color: #95a5a6;
    color: var(--light);
    margin-top: 1rem;
}

.clear-history-btn:hover { background-color: #7f8c8d; }

/* footer */
.page-footer {
    text-align: center;
    padding: 1.5rem 2rem;
    background-color: rgba(0, 0, 0, 0.05);
    border-top: 1px solid var(--gray);
    font-size: 0.9rem;
    color: var(--dark);
}

.footer-text {
    margin-bottom: 0.5rem;
}

.footer-credits {
    font-size: 0.85rem;
    color: #7f8c8d;
}

.footer-credits a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-credits a:hover {
    text-decoration: underline;
}

/* hidden class */
.hidden { display: none; }

/* input fixed to corner on scroll */
.input-section.scrolled {
    position: fixed;
    top: 20px;
    left: 20px;
    width: 280px;
    max-width: 40%;
    transform: scale(0.85);
    z-index: 1000;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.input-section.scrolled .input-label,
.input-section.scrolled .input-hint,
.input-section.scrolled .section-title,
.input-section.scrolled .error-message {
    display: none;
}

.input-section.scrolled .color-input {
    font-size: 0.95rem;
    padding: 0.75rem;
}

/* mobile phones */
@media (max-width: 480px) {
    .page-header h1 { font-size: 1.8rem; }
    .color-display { font-size: 2.5rem; min-height: 4rem; }
    .color-history { grid-template-columns: repeat(4, 1fr); }
    .color-swatch { height: 80px; }
}

/* tablets */
@media (min-width: 481px) and (max-width: 768px) {
    .page-header h1 { font-size: 2.2rem; }
    .button-group { grid-template-columns: repeat(2, 1fr); }
    .random-btn { grid-column: 1; }
    .copy-btn { grid-column: 2; }
    .reset-btn { grid-column: 1 / -1; }
}

/* big screens */
@media (min-width: 769px) {
    .page-header h1 { font-size: 2.8rem; }
    .button-group { grid-template-columns: repeat(3, 1fr); }
    .color-display { font-size: 4rem; min-height: 6rem; }
}

/* if user prefers reduced animations */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}