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

:root {
    /* Dark Mode Colors */
    --background: hsl(220, 15%, 9%);
    --foreground: hsl(0, 0%, 93%);
    --card: hsl(220, 12%, 13%);
    --card-foreground: hsl(0, 0%, 96%);
    --primary: hsl(210, 90%, 60%);
    --primary-foreground: hsl(0, 0%, 100%);
    --primary-glow: hsl(210, 90%, 70%);
    --secondary: hsl(220, 12%, 17%);
    --secondary-foreground: hsl(0, 0%, 92%);
    --muted: hsl(220, 10%, 15%);
    --muted-foreground: hsl(220, 8%, 65%);
    --accent: hsl(28, 85%, 58%);
    --accent-foreground: hsl(0, 0%, 100%);
    --border: hsl(220, 10%, 22%);
    --input: hsl(220, 10%, 18%);
    --radius: 0.75rem;

    /* Gradients */
    --gradient-primary: linear-gradient(135deg, hsl(210, 90%, 60%), hsl(200, 85%, 65%));
    --gradient-accent: linear-gradient(135deg, hsl(28, 85%, 58%), hsl(210, 90%, 60%));
    --gradient-subtle: linear-gradient(180deg, hsl(220, 15%, 10%), hsl(220, 15%, 8%));
    --gradient-card: linear-gradient(135deg, hsl(220, 12%, 14%), hsl(220, 12%, 11%));

    /* Shadows */
    --shadow-elegant: 0 10px 30px -10px hsl(210, 90%, 60%, 0.3);
    --shadow-strong: 0 20px 45px -15px hsl(210, 90%, 60%, 0.35);
    --shadow-glow: 0 0 30px hsl(210, 90%, 65%, 0.3);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--gradient-subtle);
    color: var(--foreground);
    line-height: 1.6;
    min-height: 100vh;
}

/* Header */
header {
    background: rgba(20, 20, 30, 0.85);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
}

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

.api-key-section {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.api-key-input {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    background: var(--card);
    color: var(--foreground);
    font-size: 0.875rem;
    width: 16rem;
}

.api-key-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(158, 109, 246, 0.2);
}

.api-key-input::placeholder {
    color: var(--muted-foreground);
}

.logo {
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 0.75rem;
    background: var(--gradient-accent);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-glow);
}

.logo svg {
    width: 1.25rem;
    height: 1.25rem;
    color: var(--primary-foreground);
}

.header-title h1 {
    font-size: 1.25rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.header-title p {
    font-size: 0.75rem;
    color: var(--muted-foreground);
}

/* Help modal styling */
.help-modal {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    display: flex;
    justify-content: center;
    align-items: center;
    padding-top: 10rem;
    z-index: 9999;
}

.help-content {
    background: var(--card);
    color: var(--foreground);
    padding: 1.5rem;
    border-radius: 0.75rem;
    max-width: 400px;
    width: 90%;
    text-align: left;
    box-shadow: 0 4px 12px rgba(0,0,0,0.2);
    animation: fadeIn 0.3s ease-in-out;
}

.help-content h3 {
    margin-bottom: 1rem;
    color: var(--accent);
    font-size: 1.25rem;
}

.help-content ol {
    margin-left: 1.25rem;
    margin-bottom: 1rem;
    font-size: 0.95rem;
}

.help-content a {
    color: var(--accent);
    text-decoration: underline;
}

/* Main Content */
main {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

.hero {
    text-align: center;
    margin-bottom: 3rem;
    animation: fadeIn 0.6s ease-out;
}

.hero h2 {
    font-size: clamp(2rem, 5vw, 3rem);
    font-weight: 700;
    margin-bottom: 1rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero p {
    font-size: 1.125rem;
    color: var(--muted-foreground);
    max-width: 42rem;
    margin: 0 auto;
}

.two-column {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-bottom: 4rem;
}

@media (max-width: 768px) {
    .two-column {
        grid-template-columns: 1fr;
    }

    /* Header responsive stacking */
    .header-content {
        flex-direction: column;
        align-items: center;
        text-align: center;
        gap: 1rem;
    }

    .header-left {
        flex-direction: row;
        align-items: center;
        text-align: center;
    }

    .api-key-section {
        width: 100%;
        justify-content: center;
        flex-wrap: wrap;
    }

    .api-key-input {
        width: 90%;
        max-width: 20rem;
    }

    .header-title h1 {
        font-size: 1.5rem;
    }

    .header-title p {
        font-size: 0.875rem;
    }
}

.card {
    background: var(--gradient-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 2rem;
    box-shadow: var(--shadow-elegant);
    animation: slideUp 0.6s ease-out;
}

/* Upload Section */
.upload-header {
    text-align: center;
    margin-bottom: 1.5rem;
}

.upload-icon {
    width: 4rem;
    height: 4rem;
    border-radius: 50%;
    background: var(--gradient-accent);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1rem;
    box-shadow: var(--shadow-glow);
}

.upload-icon svg {
    width: 2rem;
    height: 2rem;
    color: var(--primary-foreground);
}

.upload-header h2 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.upload-header p {
    color: var(--muted-foreground);
    font-size: 0.875rem;
}

.drop-zone {
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 3rem;
    text-align: center;
    transition: all 0.3s ease;
    cursor: pointer;
}

.drop-zone:hover,
.drop-zone.drag-over {
    border-color: var(--primary);
    background: rgba(158, 109, 246, 0.05);
    box-shadow: var(--shadow-glow);
}

.drop-zone.uploaded {
    background: rgba(91, 218, 252, 0.1);
    border-color: var(--accent);
}

.drop-zone svg {
    width: 3rem;
    height: 3rem;
    color: var(--muted-foreground);
    margin-bottom: 1rem;
}

.drop-zone.uploaded svg {
    color: var(--accent);
}

.drop-zone h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.drop-zone p {
    font-size: 0.875rem;
    color: var(--muted-foreground);
    margin-bottom: 1rem;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.625rem 1.5rem;
    border-radius: 0.5rem;
    font-weight: 500;
    font-size: 0.875rem;
    cursor: pointer;
    border: none;
    transition: all 0.3s ease;
}

.btn-gradient {
    background: var(--gradient-accent);
    color: var(--primary-foreground);
    box-shadow: var(--shadow-strong);
}

.btn-gradient:hover {
    box-shadow: var(--shadow-glow);
    transform: translateY(-2px);
}

.btn-ghost {
    background: transparent;
    color: var(--foreground);
}

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

.btn svg {
    width: 1rem;
    height: 1rem;
}

/* Chat Section */
.chat-container {
    display: flex;
    flex-direction: column;
    height: 37.5rem;
}

.chat-header {
    padding: 1rem;
    border-bottom: 1px solid var(--border);
    background: var(--gradient-subtle);
    border-radius: var(--radius) var(--radius) 0 0;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.chat-avatar {
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 50%;
    background: var(--gradient-accent);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-glow);
}

.chat-avatar svg {
    width: 1.25rem;
    height: 1.25rem;
    color: var(--primary-foreground);
}

.chat-info h3 {
    font-weight: 600;
    font-size: 0.9375rem;
}

.chat-info p {
    font-size: 0.75rem;
    color: var(--muted-foreground);
}

.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 1rem;
}

.chat-empty {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    text-align: center;
    animation: slideUp 0.6s ease-out;
}

.chat-empty svg {
    width: 3rem;
    height: 3rem;
    color: var(--muted-foreground);
    margin-bottom: 1rem;
}

.chat-empty h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.chat-empty p {
    font-size: 0.875rem;
    color: var(--muted-foreground);
    max-width: 20rem;
}

.message {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1rem;
    animation: slideUp 0.4s ease-out;
}

.message.user {
    flex-direction: row-reverse;
}

.message-avatar {
    width: 2rem;
    height: 2rem;
    border-radius: 50%;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-elegant);
}

.message.assistant .message-avatar {
    background: var(--gradient-accent);
}

.message.user .message-avatar {
    background: var(--accent);
}

.message-avatar svg {
    width: 1rem;
    height: 1rem;
    color: white;
}

.message-content {
    max-width: 80%;
    padding: 1rem;
    border-radius: var(--radius);
    font-size: 0.875rem;
    line-height: 1.5;
}

.message.assistant .message-content {
    background: var(--secondary);
}

.message.user .message-content {
    background: var(--primary);
    color: var(--primary-foreground);
    box-shadow: var(--shadow-elegant);
}

.typing-indicator {
    display: flex;
    gap: 0.25rem;
    padding: 1rem;
}

.typing-dot {
    width: 0.5rem;
    height: 0.5rem;
    background: var(--primary);
    border-radius: 50%;
    animation: bounce 1.4s infinite ease-in-out both;
}

.typing-dot:nth-child(1) { animation-delay: -0.5s; }
.typing-dot:nth-child(2) { animation-delay: -0.25s; }

.chat-input {
    padding: 1rem;
    border-top: 1px solid var(--border);
    background: var(--gradient-subtle);
    border-radius: 0 0 var(--radius) var(--radius);
    display: flex;
    gap: 0.5rem;
}

.chat-input input {
    flex: 1;
    padding: 0.625rem 1rem;
    border: 1px solid var(--input);
    border-radius: 0.5rem;
    font-size: 0.875rem;
    background: var(--card);
    color: var(--foreground);
}

.chat-input input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(158, 109, 246, 0.1);
}

.btn-icon {
    width: 2.5rem;
    height: 2.5rem;
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* Features */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
    gap: 1.5rem;
    margin-top: 4rem;
    animation: fadeIn 0.6s ease-out 0.3s both;
}

.feature-card {
    text-align: center;
    padding: 1.5rem;
    background: var(--card);
    border-radius: var(--radius);
    box-shadow: var(--shadow-elegant);
}

.feature-icon {
    width: 3rem;
    height: 3rem;
    border-radius: 50%;
    background: var(--gradient-accent);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 1rem;
    box-shadow: var(--shadow-glow);
}

.feature-icon svg {
    width: 1.5rem;
    height: 1.5rem;
    color: var(--primary-foreground);
}

.feature-card h3 {
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.feature-card p {
    font-size: 0.875rem;
    color: var(--muted-foreground);
}

/* Footer */
footer {
    border-top: 1px solid var(--border);
    margin-top: 4rem;
    padding: 1.5rem;
    text-align: center;
    font-size: 0.875rem;
    color: var(--muted-foreground);
}

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

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes bounce {
    0%, 80%, 100% {
        transform: scale(0);
    }
    40% {
        transform: scale(1);
    }
}

@keyframes spin {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

.spinner {
    width: 3rem;
    height: 3rem;
    border: 4px solid var(--primary);
    border-top-color: transparent;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 1rem;
}

/* Toast notifications */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: var(--card);
    padding: 1rem 1.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow-strong);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    animation: slideUp 0.3s ease-out;
    z-index: 1000;
}

.toast.success {
    border-left: 4px solid var(--accent);
}

.toast.error {
    border-left: 4px solid hsl(0, 84%, 60%);
}

#file-input {
    display: none;
}