/* Basic Reset and Box Sizing */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: sans-serif;
}

/* CSS Variables for Theming */
:root {
    --font-size-small: 8px;
    --font-size-normal: 14px;
    --font-size-large: 16px;
    --border-radius: 5px;
    --transition-speed: 0.3s;
}

body.dark-theme {
    --bg-primary: #1e1e1e;
    --bg-secondary: #2a2a2a;
    --bg-tertiary: #333;
    --text-primary: #e0e0e0;
    --text-secondary: #b0b0b0;
    --border-color: #444;
    --accent-color: #007bff;
    --accent-text-color: #ffffff;
    --sender-bg: #056162;
    --receiver-bg: #3a3a3a;
    --icon-color: #b0b0b0;
    --icon-hover-color: #e0e0e0;
    --modal-bg: #2a2a2a;
    --input-bg: #333;
    --input-border: #555;
    --button-bg: #007bff;
    --button-hover-bg: #0056b3;
    --button-text: #ffffff;
    --danger-color: #dc3545;
    --notification-bg: rgba(0, 0, 0, 0.8);
    --notification-text: #ffffff;
    --scrollbar-thumb: #555;
    --scrollbar-track: #333;
}

body.light-theme {
    --bg-primary: #f8f9fa;
    --bg-secondary: #ffffff;
    --bg-tertiary: #e9ecef;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --border-color: #dee2e6;
    --accent-color: #007bff;
    --accent-text-color: #ffffff;
    --sender-bg: #dcf8c6;
    --receiver-bg: #f1f0f0;
    --icon-color: #6c757d;
    --icon-hover-color: #212529;
    --modal-bg: #ffffff;
    --input-bg: #ffffff;
    --input-border: #ced4da;
    --button-bg: #007bff;
    --button-hover-bg: #0056b3;
    --button-text: #ffffff;
    --danger-color: #dc3545;
    --notification-bg: rgba(255, 255, 255, 0.9);
    --notification-text: #212529;
    --scrollbar-thumb: #adb5bd;
    --scrollbar-track: #e9ecef;
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-size: var(--font-size-normal);
    line-height: 1.5;
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

#app {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    overflow: hidden; /* Prevent body scroll when sidebar is open */
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 15px;
    background-color: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0; /* Prevent header from shrinking */
}

.header-left, .header-right {
    flex-basis: auto;
}

.header-center {
    flex-grow: 1;
    display: flex;
    justify-content: flex-start; /* Align items to start */
    align-items: center;
    gap: 10px; /* Space between controls */
    padding: 0 15px; /* Padding around center controls */
    overflow-x: auto; /* Allow scrolling if controls overflow */
    scrollbar-width: none; /* Hide scrollbar for Firefox */
    -ms-overflow-style: none; /* Hide scrollbar for IE/Edge */
}
.header-center::-webkit-scrollbar { /* Hide scrollbar for Chrome/Safari/Opera */
    display: none;
}


header button, header select {
    background: none;
    border: none;
    color: var(--icon-color);
    cursor: pointer;
    padding: 8px;
    font-size: 1.2em; /* Slightly larger icons */
    border-radius: var(--border-radius);
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

header select {
    font-size: var(--font-size-normal); /* Normal text size for select */
    padding: 5px 8px;
    background-color: var(--input-bg);
    border: 1px solid var(--input-border);
    color: var(--text-primary);
    border-radius: var(--border-radius);
}

header select option {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
}


header button:hover {
    color: var(--icon-hover-color);
    background-color: var(--bg-tertiary);
}

#new-chat-btn {
    background-color: var(--accent-color);
    color: var(--accent-text-color);
    padding: 6px 12px;
    font-size: var(--font-size-normal);
}
#new-chat-btn:hover {
    background-color: var(--button-hover-bg);
    color: var(--accent-text-color);
}
#new-chat-btn i {
    margin-right: 5px;
}

#delete-chat-btn:hover {
    color: var(--danger-color);
    background-color: var(--bg-tertiary);
}


/* Sidebar */
#sidebar {
    position: fixed;
    top: 0;
    left: -260px; /* Start off-screen */
    width: 250px;
    height: 100%;
    background-color: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    padding: 20px;
    transition: left var(--transition-speed) ease-in-out;
    z-index: 1001; /* Above overlay */
    box-shadow: 2px 0 5px rgba(0,0,0,0.2);
    display: flex;
    flex-direction: column;
}

#sidebar.active {
    left: 0;
}

#close-sidebar-btn {
    position: absolute;
    top: 10px;
    right: 10px;
    background: none;
    border: none;
    font-size: 1.8em;
    color: var(--text-secondary);
    cursor: pointer;
}
#close-sidebar-btn:hover {
    color: var(--text-primary);
}


#sidebar ul {
    list-style: none;
    margin-top: 30px;
}

#sidebar ul li a {
    display: block;
    padding: 10px 0;
    color: var(--text-primary);
    text-decoration: none;
    font-size: var(--font-size-large);
    transition: color var(--transition-speed);
}
#sidebar ul li a:hover {
    color: var(--accent-color);
}
#sidebar ul li a i {
    margin-right: 10px;
    width: 20px; /* Align icons */
    text-align: center;
}

/* Main Content */
#main-content {
    flex-grow: 1; /* Take remaining vertical space */
    display: flex;
    flex-direction: column;
    align-items: center; /* Center content horizontally */
    padding: 15px;
    overflow-y: hidden; /* Prevent main scroll, handled by chat-box */
}

.horizontal-center {
    margin: 0;
    position: absolute;
    left: 50%;
    -ms-transform: translateX(-50%);
    transform: translateX(-50%);
  }

#chat-box-container {
    width: 100%;
    max-width: 640px; /* Max width for chat */
    flex-grow: 1; /* Allow container to grow */
    display: flex; /* Use flex to manage chat-box growth */
    flex-direction: column;
     min-height: 100px; /* Minimum height before growing */
    max-height: 75vh; /* Max height relative to viewport */
    margin-bottom: 10px;
}

#chat-box {
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 10px;
    overflow-y: auto; /* Enable vertical scrollbar */
    background-color: var(--bg-tertiary);
    flex-grow: 1; /* Allow chat-box to take space within container */
    display: flex;
    flex-direction: column; /* Stack messages vertically */
    gap: 10px; /* Space between messages */
    word-wrap: break-word; /* Break long words */
}

/* Scrollbar Styling */
#chat-box::-webkit-scrollbar {
    width: 8px;
}
#chat-box::-webkit-scrollbar-track {
    background: var(--scrollbar-track);
    border-radius: 4px;
}
#chat-box::-webkit-scrollbar-thumb {
    background: var(--scrollbar-thumb);
    border-radius: 4px;
}
#chat-box::-webkit-scrollbar-thumb:hover {
    background: #777; /* Slightly lighter on hover */
}

/* Welcome Message */
.welcome-message {
    text-align: center;
    color: var(--text-secondary);
    margin: auto; /* Center vertically and horizontally */
    font-style: italic;
}


/* Input Area */
#input-area {
    width: 100%;
    max-width: 640px; /* Match chat box width */
    display: flex;
    flex-direction: column;
    flex-shrink: 0; /* Prevent shrinking */
}

#char-count {
    font-size: var(--font-size-small);
    color: var(--text-secondary);
    text-align: left;
    margin-bottom: 3px;
    padding-left: 5px;
}

#message-input {
    width: 100%;
    min-height: 50px; /* Start small */
    max-height: 200px; /* Limit growth */
    resize: vertical; /* Allow vertical resize only */
    padding: 10px;
    border: 1px solid var(--input-border);
    border-radius: var(--border-radius);
    margin-bottom: 10px;
    background-color: var(--input-bg);
    color: var(--text-primary);
    font-size: var(--font-size-normal);
}

#message-input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
}

.button-row {
    display: flex;
    gap: 10px; /* Space between buttons */
}

.button-row button {
    flex-grow: 1; /* Make buttons share space equally */
    flex-basis: 0; /* Allow buttons to grow from zero */
    padding: 10px 15px;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: var(--font-size-normal);
    transition: background-color var(--transition-speed);
    color: var(--button-text);
}
.button-row button i {
    margin-right: 5px;
}

#encrypt-btn {
    background-color: var(--accent-color);
}
#encrypt-btn:hover {
    background-color: var(--button-hover-bg);
}

#decrypt-btn {
    background-color: #5a5269;    
}
#decrypt-btn:hover {
    background-color: #6c757d;
}

#paste-btn {
    background-color: #6c757d; /* Secondary button color */
}
#paste-btn:hover {
    background-color: #5a6268;
}

/* Chat Messages */
.chat-message {
    padding: 8px 12px;
    border-radius: var(--border-radius);
    max-width: 80%; /* Limit message width */
    position: relative; /* For icon positioning */
    display: flex;
    flex-direction: column; /* Stack text and actions */
}

.message-content {
    margin-bottom: 3px;
}
.message-below-text {
    font-size: 0.8em;
    color: var(--text-secondary);
    font-style: italic;
    margin-bottom: 5px;
}


.chat-message.sender {
    background-color: var(--sender-bg);
    align-self: flex-end; /* Align right */
    margin-left: auto; /* Push to the right */
    color: var(--text-primary); /* Adjust text color if needed */
}

.chat-message.receiver {
    background-color: var(--receiver-bg);
    align-self: flex-start; /* Align left */
    margin-right: auto; /* Push to the left */
}

.message-actions {
    display: flex;
    gap: 8px;
    margin-top: 5px;
    /* position: absolute;
    top: 2px;
    right: 5px; */
    /* opacity: 0; /* Hide by default */
    /* transition: opacity 0.2s; */
}

/* .chat-message:hover .message-actions {
    opacity: 1; /* Show on hover */
/* } */

.message-actions button {
    background: none;
    border: none;
    color: var(--icon-color);
    cursor: pointer;
    font-size: 0.9em;
    padding: 2px;
}
.message-actions button:hover {
    color: var(--icon-hover-color);
}
.message-actions .delete-msg-btn:hover {
    color: var(--danger-color);
}


/* Modals (Lightboxes) */
#modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.6); /* Semi-transparent black */
    z-index: 1000;
    display: none; /* Hidden by default */
}

.modal {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: var(--modal-bg);
    padding: 25px 30px;
    border-radius: var(--border-radius);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
    z-index: 1001; /* Above overlay */
    display: none; /* Hidden by default */
    min-width: 300px;
    max-width: 90%;
    max-height: 90vh;
    overflow-y: auto;
}

.modal.active, #modal-overlay.active {
    display: block;
}

.modal-content {
    display: flex;
    flex-direction: column;
}

.modal h2 {
    margin-top: 0;
    margin-bottom: 20px;
    color: var(--text-primary);
    text-align: center;
}

.modal p {
    margin-bottom: 15px;
}

.modal label {
    display: block;
    margin-bottom: 5px;
    font-weight: bold;
    color: var(--text-secondary);
}

.modal input[type="text"],
.modal input[type="password"],
.modal select {
    width: 100%;
    padding: 10px;
    margin-bottom: 15px;
    border: 1px solid var(--input-border);
    border-radius: var(--border-radius);
    background-color: var(--input-bg);
    color: var(--text-primary);
    font-size: var(--font-size-normal);
}

.modal select option {
     background-color: var(--bg-secondary);
     color: var(--text-primary);
}

.modal input:focus, .modal select:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
}


.checkbox-container {
    display: flex;
    align-items: center;
    margin-bottom: 20px;
}
.checkbox-container input[type="checkbox"] {
    margin-right: 10px;
}
.checkbox-container label {
    margin-bottom: 0; /* Override default label margin */
    font-weight: normal;
     color: var(--text-primary);
}


.close-modal-btn {
    position: absolute;
    top: 10px;
    right: 15px;
    font-size: 1.8em;
    color: var(--text-secondary);
    cursor: pointer;
    line-height: 1;
}
.close-modal-btn:hover {
    color: var(--text-primary);
}

.modal-buttons {
    display: flex;
    justify-content: flex-end; /* Align buttons to the right */
    gap: 10px;
    margin-top: 20px;
}

.modal-buttons button {
    padding: 10px 20px;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: var(--font-size-normal);
}

.modal-buttons button[type="submit"],
.modal-buttons .close-btn, /* General close button */
#confirm-action-btn, /* Confirmation confirm */
#password-prompt-submit /* Password submit */
{
    background-color: var(--accent-color);
    color: var(--button-text);
}
.modal-buttons button[type="submit"]:hover,
.modal-buttons .close-btn:hover,
#confirm-action-btn:hover,
#password-prompt-submit:hover
{
    background-color: var(--button-hover-bg);
}

.modal-buttons .cancel-btn, /* General cancel button */
#confirm-cancel-btn, /* Confirmation cancel */
#password-prompt-cancel /* Password cancel */
{
    background-color: #6c757d;
    color: var(--button-text);
}
.modal-buttons .cancel-btn:hover,
#confirm-cancel-btn:hover,
#password-prompt-cancel:hover
{
    background-color: #5a6268;
}

/* Preferences Modal Specifics */
.preference-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-color);
}
.preference-item:last-child {
    border-bottom: none;
}

#theme-toggle {
    padding: 8px 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    cursor: pointer;
    background-color: var(--input-bg);
    color: var(--text-primary);
}
#theme-toggle i {
    margin-right: 5px;
}

/* Explanation Modal Specifics */
#explanation-modal ul {
    list-style: disc;
    margin-left: 20px;
}
#explanation-modal ul li {
    margin-bottom: 8px;
}
#explanation-modal i {
    color: var(--accent-color);
    font-style: normal; /* Prevent italics if needed */
    width: 15px;
    display: inline-block;
    text-align: center;
}


/* Notification Area */
#notification-area {
    position: fixed;
    top: 15px; /* Position below header */
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--notification-bg);
    color: var(--notification-text);
    padding: 10px 20px;
    border-radius: var(--border-radius);
    z-index: 2000; /* Above everything */
    display: none; /* Hidden by default */
    font-size: var(--font-size-normal);
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

/* Tooltips - Basic browser default using title attribute */
[title] {
    /* You could add custom tooltip styling here if needed,
       but using the native 'title' attribute is simpler */
}

/* Utility Class */
.hidden {
    display: none !important; /* Force hide */
}

/* Small screen adjustments */
@media (max-width: 600px) {
    header {
        padding: 8px 10px;
    }
    .header-center {
        padding: 0 5px; /* Less padding */
        gap: 5px; /* Less gap */
    }
    header button, header select {
        font-size: 1em; /* Slightly smaller controls on mobile */
        padding: 6px;
    }
     header select {
        font-size: 0.9em;
        padding: 4px 6px;
     }
    #new-chat-btn {
        padding: 5px 8px;
        font-size: 0.9em;
    }
    #new-chat-btn i {
        margin-right: 3px;
    }
    #new-chat-btn span {
         display: none; /* Optionally hide text on small screens */
    }


    #main-content {
        padding: 10px;
    }
    #chat-box-container {
         max-height: calc(100vh - 180px); /* Adjust max height considering header/input */
    }
    #message-input {
        min-height: 40px;
    }
    .button-row button {
        padding: 8px 10px;
        font-size: 0.9em;
    }
    .modal {
        padding: 20px;
        min-width: 280px;
    }
    .modal h2 {
        font-size: 1.2em;
    }
    .modal-buttons button {
        padding: 8px 15px;
        font-size: 0.9em;
    }

    .chat-message {
        max-width: 90%; /* Allow slightly wider messages */
    }
}