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

:root {
    /* Light mode colors */
    --bg-primary: #f5f7fa;
    --bg-secondary: #ffffff;
    --bg-tertiary: #e8ecef;
    --text-primary: #2d3748;
    --text-secondary: #718096;
    --border-color: #e2e8f0;
    --accent-color: #4299e1;
    --accent-hover: #3182ce;
    --message-sent: #4299e1;
    --message-received: #48bb78;
    --error-color: #f56565;
    --success-color: #48bb78;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

body.dark-mode {
    /* Dark mode colors */
    --bg-primary: #1a202c;
    --bg-secondary: #2d3748;
    --bg-tertiary: #374151;
    --text-primary: #f7fafc;
    --text-secondary: #a0aec0;
    --border-color: #4a5568;
    --accent-color: #63b3ed;
    --accent-hover: #4299e1;
    --message-sent: #3182ce;
    --message-received: #38a169;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
        'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Screen Management */
.screen {
    display: none;
    min-height: 100vh;
}

.screen.active {
    display: flex;
    justify-content: center;
    align-items: center;
}

.container {
    width: 100%;
    max-width: 500px;
    padding: 2rem;
}

/* Landing Screen */
.header {
    text-align: center;
    margin-bottom: 2rem;
}

.header h1 {
    font-size: 3rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.tagline {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

.landing-content {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow);
}

.info-box {
    background: var(--bg-tertiary);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 2rem;
}

.info-box p {
    margin: 0.5rem 0;
    color: var(--text-secondary);
}

.action-buttons {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.btn {
    padding: 0.875rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: center;
}

.btn-primary {
    background: var(--accent-color);
    color: white;
}

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(66, 153, 225, 0.3);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--border-color);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.divider {
    text-align: center;
    position: relative;
    margin: 1rem 0;
}

.divider span {
    background: var(--bg-secondary);
    padding: 0 1rem;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.divider::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 0;
    right: 0;
    height: 1px;
    background: var(--border-color);
    z-index: -1;
}

.join-form {
    display: flex;
    gap: 0.5rem;
}

.join-form input {
    flex: 1;
    padding: 0.875rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background: var(--bg-secondary);
    color: var(--text-primary);
    text-transform: uppercase;
    text-align: center;
    letter-spacing: 0.1em;
}

.join-form input:focus {
    outline: none;
    border-color: var(--accent-color);
}

.error-message {
    margin-top: 1rem;
    padding: 0.75rem;
    background: rgba(245, 101, 101, 0.1);
    border: 1px solid var(--error-color);
    border-radius: 8px;
    color: var(--error-color);
    font-size: 0.875rem;
    display: none;
}

.error-message.show {
    display: block;
}

.landing-footer {
    margin-top: 2rem;
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* Loading Screen */
.loading-content {
    text-align: center;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 4px solid var(--border-color);
    border-top-color: var(--accent-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 2rem;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

#room-code-display {
    font-size: 2rem;
    font-weight: bold;
    color: var(--accent-color);
    letter-spacing: 0.3em;
    margin: 1rem 0;
}

#waiting-text {
    color: var(--text-secondary);
    margin-top: 1rem;
}

/* Chat Screen */
#chat-screen.active {
    display: block;
}

.chat-container {
    height: 100vh;
    display: flex;
    flex-direction: column;
    background: var(--bg-secondary);
}

.chat-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
    background: var(--bg-secondary);
    border-bottom: 2px solid var(--border-color);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.header-left {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.header-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.header-left h2 {
    font-size: 1.5rem;
}

.chat-timer {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    padding: 0.25rem 0.75rem;
    background: var(--bg-tertiary);
    border-radius: 12px;
    font-size: 0.75rem;
    color: var(--text-secondary);
    font-weight: 600;
}

#timer-display {
    font-variant-numeric: tabular-nums;
    min-width: 2.5rem;
    text-align: center;
}

.status {
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
}

.status.connected {
    background: rgba(72, 187, 120, 0.2);
    color: var(--success-color);
}

.status.waiting {
    background: rgba(237, 137, 54, 0.2);
    color: #ed8936;
}

.status.disconnected {
    background: rgba(245, 101, 101, 0.2);
    color: var(--error-color);
}

.header-right {
    display: flex;
    gap: 0.5rem;
}

.icon-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 8px;
    transition: background 0.2s ease;
}

.icon-btn:hover {
    background: var(--bg-tertiary);
}

/* Messages Container */
.messages-container {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
    background: var(--bg-primary);
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.system-message {
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.875rem;
    padding: 0.75rem;
    background: var(--bg-tertiary);
    border-radius: 8px;
    margin-bottom: 1rem;
}

.message {
    display: flex;
    gap: 0.5rem;
    animation: slideIn 0.2s ease;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.message.sent {
    justify-content: flex-end;
}

.message-bubble {
    max-width: 70%;
    padding: 0.75rem 1rem;
    border-radius: 16px;
    word-wrap: break-word;
    white-space: pre-wrap;
}

.message.sent .message-bubble {
    background: var(--message-sent);
    color: white;
    border-bottom-right-radius: 4px;
}

.message.received .message-bubble {
    background: var(--message-received);
    color: white;
    border-bottom-left-radius: 4px;
}

.message-time {
    font-size: 0.7rem;
    opacity: 0.7;
    margin-top: 0.25rem;
}

/* Typing Indicator */
.typing-indicator {
    padding: 0.5rem 1.5rem;
    background: var(--bg-secondary);
    color: var(--text-secondary);
    font-size: 0.875rem;
    display: none;
    align-items: center;
    gap: 0.5rem;
}

.typing-indicator.show {
    display: flex;
}

.dots span {
    animation: blink 1.4s infinite;
}

.dots span:nth-child(2) {
    animation-delay: 0.2s;
}

.dots span:nth-child(3) {
    animation-delay: 0.4s;
}

@keyframes blink {
    0%, 60%, 100% {
        opacity: 0;
    }
    30% {
        opacity: 1;
    }
}

/* Message Input */
.message-input-container {
    display: flex;
    gap: 0.5rem;
    padding: 1rem 1.5rem;
    background: var(--bg-secondary);
    border-top: 2px solid var(--border-color);
}

#message-input {
    flex: 1;
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: 20px;
    font-size: 1rem;
    font-family: inherit;
    background: var(--bg-primary);
    color: var(--text-primary);
    resize: none;
    max-height: 120px;
}

#message-input:focus {
    outline: none;
    border-color: var(--accent-color);
}

#send-btn {
    padding: 0.75rem 1.5rem;
    border-radius: 20px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    .header h1 {
        font-size: 2rem;
    }

    .landing-content {
        padding: 1.5rem;
    }

    .join-form {
        flex-direction: column;
    }

    .message-bubble {
        max-width: 85%;
    }

    .chat-header {
        padding: 0.75rem 1rem;
    }

    .header-left {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }

    .header-left h2 {
        font-size: 1.25rem;
    }

    .chat-timer {
        font-size: 0.7rem;
        padding: 0.2rem 0.6rem;
    }

    .messages-container {
        padding: 1rem;
    }

    .message-input-container {
        padding: 0.75rem 1rem;
    }
}

/* Scrollbar Styling */
.messages-container::-webkit-scrollbar {
    width: 8px;
}

.messages-container::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

.messages-container::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.messages-container::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}