/* ============================================
   CSS Custom Properties (Theme Variables)
   ============================================ */
:root {
    /* Colors */
    --color-primary: #4a90e2;
    --color-primary-hover: #3a7bc8;
    --color-success: #2ecc71;
    --color-warning: #f39c12;
    --color-text: #333;
    --color-text-light: #555;
    --color-text-muted: #828282;
    --color-text-placeholder: #999;
    --color-bg-main: #ffffff;
    --color-bg-sidebar: #f8f9fa;
    --color-bg-locked: #f0f0f0;
    --color-bg-locked-hover: #e8e8e8;
    --color-bg-button-secondary: #e0e0e0;
    --color-bg-button-secondary-hover: #d0d0d0;
    --color-bg-highlight: #fffacd;
    --color-bg-hover: #f0f7ff;
    --color-border: #e0e0e0;
    --color-border-input: #d0d0d0;
    --color-border-highlight: var(--color-primary);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-xxl: 4rem;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    --font-size-base: 0.95rem;
    --font-size-small: 0.85rem;
    --font-size-reading: 20px;
    --font-size-title: 1.5rem;
    --line-height-base: 1.6;
    --line-height-reading: 1.7;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 6px;
    --radius-lg: 8px;
    
    /* Transitions */
    --transition-fast: 0.2s;
    --transition-base: 0.3s;
    
    /* Animation Durations */
    --animation-pulse: 1.5s;
    --animation-content-pulse: 0.6s;
}

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

body {
    font-family: var(--font-family);
    min-height: 100vh;
    overflow-x: hidden;
}

/* ============================================
   Layout: Container
   ============================================ */
.container {
    display: flex;
    min-height: 100vh;
}

/* Mobile-first: stack vertically on small screens */
@media (max-width: 768px) {
    .container {
        flex-direction: column;
        min-height: auto;
    }
}

/* ============================================
   Component: Sidebar
   ============================================ */
.sidebar {
    width: 30%;
    min-width: 280px;
    max-width: 400px;
    padding: var(--spacing-xl);
    background-color: var(--color-bg-sidebar);
    border-right: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    overflow-y: auto;
    position: sticky;
    top: 0;
    height: 100vh;
    align-self: flex-start;
}

@media (max-width: 768px) {
    .sidebar {
        width: 100%;
        max-width: none;
        min-width: 0;
        height: auto;
        padding: var(--spacing-lg);
        border-right: none;
        border-bottom: 1px solid var(--color-border);
        position: sticky;
        top: 0;
        z-index: 100;
        box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    }
    
    .sidebar.collapsed .sidebar-content {
        display: none;
    }
    
    .sidebar.collapsed {
        padding: var(--spacing-md) var(--spacing-lg);
    }
}

.sidebar h1 {
    font-size: var(--font-size-title);
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: var(--spacing-xs);
}

@media (max-width: 768px) {
    .sidebar h1 {
        font-size: 1.25rem;
        text-align: center;
        margin-bottom: 0;
    }
}

/* ============================================
   Component: Sidebar Header (Mobile Toggle)
   ============================================ */
.sidebar-header {
    display: none;
}

@media (max-width: 768px) {
    .sidebar-header {
        display: flex;
        align-items: center;
        justify-content: space-between;
        margin-bottom: var(--spacing-md);
    }
    
    .sidebar-header h1 {
        flex: 1;
    }
    
    .sidebar.collapsed .sidebar-header {
        margin-bottom: 0;
    }
}

.toggle-btn {
    display: none;
}

@media (max-width: 768px) {
    .toggle-btn {
        display: flex;
        align-items: center;
        justify-content: center;
        width: 32px;
        height: 32px;
        min-width: 32px;
        min-height: 32px;
        flex-shrink: 0;
        padding: 0;
        background: var(--color-primary);
        color: white;
        border: none;
        border-radius: 50%;
        cursor: pointer;
        transition: all var(--transition-fast);
        box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    }
    
    .toggle-btn:hover {
        background-color: var(--color-primary-hover);
        box-shadow: 0 2px 6px rgba(0, 0, 0, 0.15);
    }
    
    .toggle-btn:active {
        transform: scale(0.9);
    }
    
    .toggle-icon {
        font-size: 0.75rem;
        line-height: 1;
        transition: transform var(--transition-base);
    }
    
    .sidebar.collapsed .toggle-icon {
        transform: rotate(-90deg);
    }
}

/* ============================================
   Component: Sidebar Content
   ============================================ */
.sidebar-content {
    display: contents;
}

@media (max-width: 768px) {
    .sidebar-content {
        display: flex;
        flex-direction: column;
        gap: var(--spacing-md);
        transition: all var(--transition-base);
    }
}

/* ============================================
   Component: Input Text
   ============================================ */
#inputText {
    flex: 1;
    padding: var(--spacing-md);
    border: 1px solid var(--color-border-input);
    border-radius: var(--radius-lg);
    font-size: var(--font-size-base);
    font-family: inherit;
    background-color: var(--color-bg-main);
    transition: border-color var(--transition-fast);
    overflow-y: auto;
    white-space: pre-wrap;
    word-wrap: break-word;
    min-height: 150px;
    max-height: 300px;
}

@media (max-width: 768px) {
    #inputText {
        min-height: 120px;
        max-height: 200px;
        font-size: 16px; /* Prevents iOS zoom on focus */
    }
}

#inputText:empty:before {
    content: attr(data-placeholder);
    color: var(--color-text-placeholder);
}

#inputText[contenteditable="false"] {
    background-color: var(--color-bg-locked);
    cursor: pointer;
}

#inputText[contenteditable="false"]:hover {
    background-color: var(--color-bg-locked-hover);
}

#inputText:focus {
    outline: none;
    border-color: var(--color-primary);
}

#inputText:focus:before {
    content: none;
}

/* ============================================
   Component: Input Tooltip
   ============================================ */
.input-tooltip {
    font-size: var(--font-size-small);
    color: var(--color-bg-main);
    background-color: var(--color-primary);
    padding: var(--spacing-xs) var(--spacing-md);
    text-align: center;
    border-radius: var(--radius-md);
    margin-top: calc(-1 * var(--spacing-xs));
    animation: fadeIn var(--transition-fast);
}

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

/* ============================================
   Component: Voice Selector
   ============================================ */
.voice-selector {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.voice-selector label {
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--color-text-light);
}

#voiceSelect {
    padding: var(--spacing-xs);
    border: 1px solid var(--color-border-input);
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-family: inherit;
    background-color: var(--color-bg-main);
    cursor: pointer;
    transition: border-color var(--transition-fast);
    min-height: 44px; /* Touch-friendly */
}

@media (max-width: 768px) {
    #voiceSelect {
        font-size: 16px; /* Prevents iOS zoom */
        min-height: 48px;
    }
}

#voiceSelect:focus {
    outline: none;
    border-color: var(--color-primary);
}

/* ============================================
   Component: Speed Control
   ============================================ */
.speed-control {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.speed-control label {
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--color-text-light);
}

#speedSlider {
    width: 100%;
    cursor: pointer;
    min-height: 44px; /* Touch-friendly */
}

@media (max-width: 768px) {
    #speedSlider {
        min-height: 48px;
    }
}

/* ============================================
   Component: Controls (Buttons)
   ============================================ */
.controls {
    display: flex;
    gap: var(--spacing-sm);
}

button {
    flex: 1;
    padding: var(--spacing-sm) var(--spacing-md);
    border: none;
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    min-height: 44px; /* Touch-friendly minimum */
}

.toggle-btn {
    flex: 0 0 auto !important; /* Override the flex: 1 from button */
}

@media (max-width: 768px) {
    button {
        min-height: 48px;
        font-size: 1rem;
        padding: var(--spacing-md) var(--spacing-lg);
    }
}

#readBtn {
    background-color: var(--color-primary);
    color: white;
}

#readBtn:hover {
    background-color: var(--color-primary-hover);
}

#readBtn.playing {
    background-color: var(--color-success);
}

#readBtn.waiting {
    background-color: var(--color-warning);
    color: white;
    animation: pulse-button var(--animation-pulse) ease-in-out infinite;
}

@keyframes pulse-button {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.6;
    }
}

#stopBtn {
    background-color: var(--color-bg-button-secondary);
    color: var(--color-text);
}

#stopBtn:hover {
    background-color: var(--color-bg-button-secondary-hover);
}

button:active {
    transform: translateY(1px);
}

/* ============================================
   Component: Reading Area
   ============================================ */
.reading-area {
    flex: 1;
    padding: var(--spacing-xxl) var(--spacing-xl);
    overflow-y: auto;
    background-color: var(--color-bg-main);
    display: flex;
    justify-content: center;
    min-height: 400px;
}

@media (max-width: 768px) {
    .reading-area {
        padding: var(--spacing-lg) var(--spacing-md);
        min-height: 300px;
    }
}

.reading-area > div,
.reading-area > p {
    max-width: 700px;
    width: 100%;
    text-align: center;
}

.reading-area .placeholder {
    color: var(--color-text-placeholder);
    font-style: italic;
}

.reading-area .content {
    font-size: var(--font-size-reading);
    line-height: var(--line-height-reading);
    color: #222;
    text-align: left;
}

@media (max-width: 768px) {
    .reading-area .content {
        font-size: 18px;
        line-height: 1.8;
    }
}

.reading-area .content p:last-child {
    margin-bottom: 0;
}

.reading-area .content .clickable-paragraph {
    cursor: pointer;
    transition: background-color var(--transition-fast);
    padding: var(--spacing-xs);
    margin-left: calc(-1 * var(--spacing-xs));
    margin-right: calc(-1 * var(--spacing-xs));
    border-radius: var(--radius-sm);
    -webkit-tap-highlight-color: transparent; /* Remove iOS tap highlight */
}

@media (max-width: 768px) {
    .reading-area .content .clickable-paragraph {
        padding: var(--spacing-sm);
        margin-left: calc(-1 * var(--spacing-sm));
        margin-right: calc(-1 * var(--spacing-sm));
        margin-bottom: var(--spacing-sm);
    }
}

.reading-area .content .clickable-paragraph:hover {
    background-color: var(--color-bg-hover);
}

.reading-area .content .currently-reading {
    background-color: var(--color-bg-highlight);
    border-left: 4px solid var(--color-border-highlight);
    padding-left: calc(var(--spacing-xs) - 4px);
}

.reading-area .content span[aria-hidden="true"] {
    color: var(--color-text-muted);
}

/* ============================================
   Animation: Content Pulse
   ============================================ */
@keyframes pulse {
    0%, 100% {
        background-color: var(--color-bg-main);
    }
    50% {
        background-color: var(--color-bg-hover);
    }
}

.reading-area.pulse {
    animation: pulse var(--animation-content-pulse) ease-in-out;
}