:root {
    --primary-color: #10a37f;
    --primary-hover: #0d8a6b;
    --danger-color: #ef4444;
    --background: #ffffff;
    --surface: #f7f7f8;
    --text-primary: #0d0d0d;
    --text-secondary: #676767;
    --border-color: #d9d9e3;
    --hover-bg: #f7f7f8;
    --user-message-bg: #f4f4f4;
    --assistant-message-bg: #ffffff;
    --header-bg: rgba(255, 255, 255, 0.95);
    --input-bg: #ffffff;
    --shadow: rgba(0, 0, 0, 0.05);
    --shadow-lg: rgba(0, 0, 0, 0.1);
    --card-bg: #ffffff;
    --button-bg: #0d0d0d;
    --button-text: #ffffff;
}

[data-theme="dark"] {
    --background: #1a1a1a;
    --surface: #2a2a2a;
    --text-primary: #ececec;
    --text-secondary: #b4b4b4;
    --border-color: #3e3e3e;
    --hover-bg: #2f2f2f;
    --user-message-bg: #2f2f2f;
    --assistant-message-bg: #2a2a2a;
    --header-bg: rgba(26, 26, 26, 0.95);
    --input-bg: #2a2a2a;
    --shadow: rgba(0, 0, 0, 0.3);
    --shadow-lg: rgba(0, 0, 0, 0.5);
    --card-bg: #2a2a2a;
    --button-bg: #ffffff;
    --button-text: #0d0d0d;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    transition: background-color 0.3s ease, color 0.3s ease;
    overflow-x: hidden;
}

/* Header */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: var(--header-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: all 0.3s ease;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    max-width: 100%;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.35rem;
    border: none;
    background: transparent;
    padding: 0.25rem 0.5rem;
    margin: -0.25rem -0.5rem;
    border-radius: 999px;
    cursor: pointer;
    transition: background-color 0.2s ease, transform 0.2s ease;
}

.logo:hover {
    background: var(--hover-bg);
}

.logo:active {
    transform: scale(0.98);
}

.logo:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

.logo-text {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.header-actions {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.btn-header {
    padding: 0.5rem 1rem;
    border-radius: 20px;
    border: none;
    background: transparent;
    color: var(--text-primary);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.btn-header:hover {
    background-color: var(--hover-bg);
}

.btn-signup {
    background-color: var(--button-bg);
    color: var(--button-text);
}

.btn-signup:hover {
    background-color: var(--button-bg);
    opacity: 0.9;
}

.btn-icon {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    border: none;
    background: transparent;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background-color 0.2s ease;
    font-size: 1rem;
}

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

/* User Menu */
.logged-out-actions {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.logged-in-actions {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.user-greeting {
    font-size: 0.95rem;
    color: var(--text-primary);
    font-weight: 500;
    padding: 0.5rem 1rem;
    background: var(--surface);
    border-radius: 20px;
}

/* Main Content */
.main-content {
    padding-top: 60px;
    min-height: 100vh;
}

/* Welcome Screen */
.welcome-screen {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: calc(100vh - 60px);
    padding: 2rem 1rem;
}

.welcome-screen.hidden {
    display: none;
}

.welcome-content {
    text-align: center;
    max-width: 700px;
    width: 100%;
}

.welcome-title {
    font-size: 2.15rem;
    font-weight: 600;
    margin-bottom: 2.5rem;
    color: var(--text-primary);
    letter-spacing: -0.03em;
}

/* Suggestion Cards */
.suggestion-cards {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.75rem;
    margin-bottom: 2.5rem;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.suggestion-card {
    background: var(--card-bg);
    border: 1.5px solid var(--border-color);
    border-radius: 14px;
    padding: 1rem 1.25rem;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    text-align: left;
    position: relative;
    overflow: hidden;
}

.suggestion-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-color), transparent);
    opacity: 0;
    transition: opacity 0.2s ease;
}

.suggestion-card:hover::before {
    opacity: 1;
}

.suggestion-card:hover {
    background: var(--hover-bg);
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 8px 16px var(--shadow);
}

.suggestion-card:active {
    transform: translateY(0);
}

.suggestion-card p {
    margin: 0;
    color: var(--text-secondary);
    font-size: 0.84rem;
    line-height: 1.4;
    font-weight: 400;
}

.suggestion-card:hover p {
    color: var(--text-primary);
}

/* Input Wrapper Center (for welcome screen) */
.input-wrapper-center {
    position: relative;
    background: var(--input-bg);
    border: 2px solid var(--border-color);
    border-radius: 30px;
    padding: 0.75rem 1rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    max-width: 700px;
    margin: 0 auto 1.5rem;
    box-shadow: 0 4px 12px var(--shadow);
    transition: all 0.2s ease;
}

.input-wrapper-center:focus-within {
    border-color: var(--primary-color);
    box-shadow: 0 4px 20px rgba(16, 163, 127, 0.15);
}

.message-input-center {
    flex: 1;
    border: none;
    background: transparent;
    color: var(--text-primary);
    font-size: 0.94rem;
    outline: none;
    padding: 0.5rem 0;
    font-family: inherit;
}

.message-input-center::placeholder {
    color: var(--text-secondary);
}

.send-button-welcome {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    border: none;
    background: var(--border-color);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    font-size: 1.1rem;
    font-weight: bold;
    flex-shrink: 0;
}

.send-button-welcome:disabled {
    background: var(--border-color);
    cursor: not-allowed;
    opacity: 0.5;
}

.send-button-welcome:not(:disabled) {
    background: var(--button-bg);
    color: var(--button-text);
}

.send-button-welcome:not(:disabled):hover {
    transform: scale(1.05);
    box-shadow: 0 4px 12px var(--shadow-lg);
}

.send-button-welcome:not(:disabled):active {
    transform: scale(0.95);
}

/* Chat Container */
.chat-container {
    max-width: 750px;
    margin: 0 auto;
    padding: 2rem 1rem 180px;
}

.chat-container.hidden {
    display: none;
}

.chat-container:not(.hidden) ~ .welcome-screen {
    display: none;
}

.message {
    margin-bottom: 1.5rem;
    display: flex;
    flex-direction: column;
    animation: fadeIn 0.3s ease;
}

.user-message {
    align-items: flex-end;
}

.assistant-message {
    align-items: flex-start;
}

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

.message-content {
    max-width: 70%;
}

.message-text {
    line-height: 1.6;
    white-space: pre-wrap;
    word-wrap: break-word;
    overflow-wrap: anywhere;
    padding: 0.875rem 1.125rem;
    border-radius: 20px;
    font-size: 0.88rem;
}

.message-text p,
.message-text ol {
    margin: 0;
}

.message-text p + p,
.message-text p + ol,
.message-text ol + p,
.message-text ol + ol {
    margin-top: 0.75rem;
}

.message-text ol {
    padding-left: 1.25rem;
}

.message-text li + li {
    margin-top: 0.35rem;
}

.message-text a {
    color: var(--primary-color);
    text-decoration: none;
}

.message-text a:hover {
    text-decoration: underline;
}

.user-message .message-text {
    background: var(--user-message-bg);
    color: var(--text-primary);
    border-bottom-right-radius: 4px;
}

.assistant-message .message-text {
    background: var(--assistant-message-bg);
    color: var(--text-primary);
    border-bottom-left-radius: 4px;
    border: 1.5px solid var(--border-color);
}

/* Typing Indicator */
.typing-indicator {
    display: flex;
    gap: 0.4rem;
    padding: 0.5rem 0;
}

.typing-dot {
    width: 8px;
    height: 8px;
    background: var(--text-secondary);
    border-radius: 50%;
    animation: typing 1.4s infinite;
}

.typing-dot:nth-child(2) {
    animation-delay: 0.2s;
}

.typing-dot:nth-child(3) {
    animation-delay: 0.4s;
}

@keyframes typing {
    0%, 60%, 100% {
        opacity: 0.3;
        transform: translateY(0);
    }
    30% {
        opacity: 1;
        transform: translateY(-6px);
    }
}

/* Input Area (for chat mode) */
.input-area {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: linear-gradient(to top, var(--background) 80%, transparent);
    padding: 2rem 0 1.25rem;
    z-index: 100;
    display: none;
}

.input-area.active {
    display: block;
}

.input-wrapper {
    max-width: 750px;
    margin: 0 auto;
    background: var(--input-bg);
    border-radius: 28px;
    border: 2px solid var(--border-color);
    padding: 0.75rem 1rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    box-shadow: 0 4px 12px var(--shadow);
    transition: all 0.2s ease;
}

.input-wrapper:focus-within {
    border-color: var(--primary-color);
    box-shadow: 0 4px 20px rgba(16, 163, 127, 0.15);
}

.input-tools {
    display: flex;
    gap: 0.25rem;
}

.tool-btn {
    width: 32px;
    height: 32px;
    border-radius: 8px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background-color 0.2s ease;
    font-size: 1rem;
}

.tool-btn:hover {
    background-color: var(--hover-bg);
}

.message-input {
    flex: 1;
    border: none;
    background: transparent;
    color: var(--text-primary);
    font-size: 0.94rem;
    outline: none;
    padding: 0.5rem 0;
    line-height: 1.5;
    font-family: inherit;
}

.message-input::placeholder {
    color: var(--text-secondary);
}

.send-button {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    border: none;
    background: var(--border-color);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    font-size: 1.1rem;
    font-weight: bold;
    flex-shrink: 0;
}

.send-button:disabled {
    background: var(--border-color);
    cursor: not-allowed;
    opacity: 0.5;
}

.send-button:not(:disabled) {
    background: var(--button-bg);
    color: var(--button-text);
}

.send-button:not(:disabled):hover {
    transform: scale(1.05);
    box-shadow: 0 4px 12px var(--shadow-lg);
}

.send-button:not(:disabled):active {
    transform: scale(0.95);
}

.input-footer {
    text-align: center;
    margin-top: 0.75rem;
    font-size: 0.7rem;
    color: var(--text-secondary);
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

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

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

/* Responsive */
@media (max-width: 768px) {
    .welcome-title {
        font-size: 1.75rem;
    }

    .suggestion-cards {
        gap: 0.5rem;
        margin-bottom: 1.5rem;
    }

    .suggestion-card {
        padding: 0.65rem 0.85rem;
    }

    .suggestion-card p {
        font-size: 0.8125rem;
    }

    .suggestion-card:nth-child(3),
    .suggestion-card:nth-child(4) {
        display: none;
    }

    .header-content {
        padding: 0.65rem 1rem;
    }

    .btn-header {
        padding: 0.4rem 0.75rem;
        font-size: 0.85rem;
    }

    .input-wrapper-center {
        margin: 0 1rem 1.5rem;
    }

    .input-wrapper {
        margin: 0 1rem;
    }
}

/* Footer */
.footer {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: linear-gradient(to top, var(--background) 70%, transparent);
    padding: 1.25rem;
    text-align: center;
    z-index: 50;
}

.footer-text {
    font-size: 0.8rem;
}

.developer-credit {
    font-size: 0.82rem;
}

.footer.hidden {
    display: none;
}

.footer-text {
    font-size: 0.75rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.footer-text a {
    color: var(--text-secondary);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: all 0.2s ease;
}

.footer-text a:hover {
    color: var(--text-primary);
    border-bottom-color: var(--text-primary);
}

.developer-credit {
    font-size: 0.7rem;
    color: var(--text-secondary);
    margin-top: 0.5rem;
}

.developer-credit strong {
    color: var(--primary-color);
    font-weight: 600;
}

/* Code blocks (for future enhancements) */
pre {
    background: var(--surface);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1rem;
    overflow-x: auto;
    margin: 1rem 0;
}

code {
    font-family: 'Courier New', monospace;
    font-size: 0.9rem;
}