:root {
    --bg-color: #f0f2f5;
    --text-color: #333;
    --header-bg: #fff;
    --chat-bg: #fff;
    --user-msg-bg: #dcf8c6;
    --ai-msg-bg: #f1f0f0;
    --input-bg: #fff;
    --btn-bg: #007bff;
    --btn-text: #fff;
    --border-color: #ddd;
}

.dark-mode {
    --bg-color: #121212;
    --text-color: #e0e0e0;
    --header-bg: #1e1e1e;
    --chat-bg: #1e1e1e;
    --user-msg-bg: #2b5278;
    --ai-msg-bg: #3a3a3a;
    --input-bg: #2c2c2c;
    --btn-bg: #0056b3;
    --border-color: #444;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    margin: 0;
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
}

#app {
    width: 100%;
    max-width: 700px;
    height: 90vh;
    max-height: 800px;
    display: flex;
    flex-direction: column;
    background: var(--chat-bg);
    border-radius: 16px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    overflow: hidden;
}

header {
    padding: 1rem;
    background-color: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.header-content {
    text-align: left;
}

.header-buttons {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

#lang-switcher {
    background-color: var(--input-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.5rem;
    cursor: pointer;
}

#teach-ai-btn {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 18px;
    padding: 0.5rem 1rem;
    cursor: pointer;
    color: var(--text-color);
    font-weight: bold;
    transition: background-color 0.2s;
}

#teach-ai-btn:hover {
    background-color: var(--ai-msg-bg);
}

header h1 {
    margin: 0;
    font-size: 1.5rem;
}

header p {
    margin: 0;
    font-size: 0.8rem;
    color: #888;
}

#theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    cursor: pointer;
    font-size: 1.5rem;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: background-color 0.2s, border-color 0.2s;
}

#theme-toggle:hover {
    background-color: var(--ai-msg-bg);
}

#chat-container {
    flex-grow: 1;
    padding: 1rem;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
}

.message {
    padding: 0.75rem 1rem;
    border-radius: 18px;
    margin-bottom: 0.5rem;
    max-width: 75%;
    line-height: 1.4;
}

.user-message {
    background-color: var(--user-msg-bg);
    align-self: flex-end;
    border-bottom-right-radius: 4px;
}

.ai-message {
    background-color: var(--ai-msg-bg);
    align-self: flex-start;
    border-bottom-left-radius: 4px;
    position: relative;
    display: flex;
    align-items: center;
}

.share-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1rem;
    padding: 0.5rem;
    margin-left: 0.5rem;
    opacity: 0;
    transition: opacity 0.2s;
}

.ai-message:hover .share-btn {
    opacity: 0.7;
}

.share-btn:hover {
    opacity: 1 !important;
}

#typing-indicator {
    font-style: italic;
    color: #888;
    animation: blink 1.5s infinite;
}

@keyframes blink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

footer {
    display: flex;
    padding: 1rem;
    border-top: 1px solid var(--border-color);
    background-color: var(--header-bg);
}

#user-input {
    flex-grow: 1;
    border: 1px solid var(--border-color);
    border-radius: 18px;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    background-color: var(--input-bg);
    color: var(--text-color);
}

#user-input:focus {
    outline: none;
    border-color: var(--btn-bg);
}

#send-btn {
    margin-left: 0.5rem;
    padding: 0.75rem 1.5rem;
    border: none;
    background-color: var(--btn-bg);
    color: var(--btn-text);
    border-radius: 18px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: bold;
    transition: background-color 0.2s;
}

#send-btn:hover {
    background-color: #0056b3;
}

/* Responsive Design */
@media (max-width: 768px) {
    #app {
        height: 100vh;
        max-height: none;
        border-radius: 0;
    }
}

/* Modal Styles */
#teach-modal.modal-hidden {
    display: none;
}

#teach-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal-content {
    background-color: var(--header-bg);
    padding: 2rem;
    border-radius: 12px;
    width: 90%;
    max-width: 500px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
    position: relative;
    color: var(--text-color);
}

.close-button {
    position: absolute;
    top: 1rem;
    right: 1rem;
    font-size: 1.5rem;
    cursor: pointer;
    color: #888;
}

#teach-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

#teach-form label {
    font-weight: bold;
}

#teach-form input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background-color: var(--input-bg);
    color: var(--text-color);
}

#submit-teach {
    padding: 0.75rem;
    border: none;
    border-radius: 8px;
    background-color: var(--btn-bg);
    color: var(--btn-text);
    font-weight: bold;
    cursor: pointer;
}

#teach-response {
    margin-top: 1rem;
    text-align: center;
    font-weight: bold;
}