/* CSS Variables for theming */
:root {
    /* Light theme (default) */
    --bg-gradient-start: #667eea;
    --bg-gradient-end: #764ba2;
    --container-bg: #ffffff;
    --container-shadow: rgba(0, 0, 0, 0.2);
    --text-primary: #333333;
    --text-secondary: #666666;
    --text-muted: #999999;
    --input-bg: #ffffff;
    --input-border: #e0e0e0;
    --input-focus-shadow: rgba(102, 126, 234, 0.2);
    --accent-color: #667eea;
    --accent-hover: #764ba2;
    --link-color: #667eea;
    --success-bg: #d4edda;
    --success-color: #155724;
    --success-border: #c3e6cb;
    --error-bg: #f8d7da;
    --error-color: #721c24;
    --error-border: #f5c6cb;
}

[data-theme="dark"] {
    /* Dark theme */
    --bg-gradient-start: #0f0c29;
    --bg-gradient-end: #302b63;
    --container-bg: #1a1a2e;
    --container-shadow: rgba(0, 0, 0, 0.5);
    --text-primary: #e8e8e8;
    --text-secondary: #b0b0b0;
    --text-muted: #808080;
    --input-bg: #16213e;
    --input-border: #3a3a5c;
    --input-focus-shadow: rgba(127, 90, 240, 0.3);
    --accent-color: #7f5af0;
    --accent-hover: #a78bfa;
    --link-color: #a78bfa;
    --success-bg: rgba(46, 213, 115, 0.2);
    --success-color: #2ed573;
    --success-border: #2ed573;
    --error-bg: rgba(255, 71, 87, 0.2);
    --error-color: #ff4757;
    --error-border: #ff4757;
}

* {
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    margin: 0;
    padding: 20px;
    background: linear-gradient(135deg, var(--bg-gradient-start) 0%, var(--bg-gradient-end) 100%);
    min-height: 100vh;
    transition: background 0.4s ease;
}

/* Back link */
.back-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: rgba(255, 255, 255, 0.9);
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    padding: 10px 16px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
    margin-bottom: 20px;
}

.back-link:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateX(-3px);
}

.back-link svg {
    width: 16px;
    height: 16px;
}

.container {
    max-width: 450px;
    margin: 0 auto;
    padding: 35px;
    background-color: var(--container-bg);
    border-radius: 16px;
    box-shadow: 0 10px 40px var(--container-shadow);
    transition: all 0.4s ease;
}

[data-theme="dark"] .container {
    border: 1px solid rgba(127, 90, 240, 0.2);
}

.container h2 {
    margin: 0 0 25px;
    color: var(--text-primary);
    font-size: 24px;
    font-weight: 700;
    text-align: center;
}

.form-group {
    margin-bottom: 20px;
}

label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: var(--text-primary);
    font-size: 14px;
    transition: color 0.4s ease;
}

select, input[type="text"] {
    width: 100%;
    padding: 14px 16px;
    font-size: 16px;
    border: 2px solid var(--input-border);
    border-radius: 10px;
    background-color: var(--input-bg);
    color: var(--text-primary);
    transition: all 0.3s ease;
    font-family: inherit;
}

select:focus, input[type="text"]:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px var(--input-focus-shadow);
}

input[type="text"]::placeholder {
    color: var(--text-muted);
}

select option {
    background-color: var(--input-bg);
    color: var(--text-primary);
    padding: 10px;
}

select option:disabled {
    color: var(--text-muted);
    font-style: italic;
}

button {
    width: 100%;
    padding: 14px 24px;
    font-size: 16px;
    font-weight: 600;
    background: linear-gradient(135deg, var(--accent-color) 0%, var(--accent-hover) 100%);
    color: #fff;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 10px;
    font-family: inherit;
}

button:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.4);
}

[data-theme="dark"] button:hover:not(:disabled) {
    box-shadow: 0 6px 25px rgba(127, 90, 240, 0.5);
}

button:active:not(:disabled) {
    transform: translateY(0);
}

button:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.additional-fields {
    display: none;
}

#chatFields {
    display: block;
}

.success-message {
    background-color: var(--success-bg);
    color: var(--success-color);
    padding: 14px 18px;
    border-radius: 10px;
    margin-bottom: 20px;
    border: 1px solid var(--success-border);
    font-weight: 500;
}

.error-message {
    background-color: var(--error-bg);
    color: var(--error-color);
    padding: 14px 18px;
    border-radius: 10px;
    margin-bottom: 20px;
    border: 1px solid var(--error-border);
    font-weight: 500;
}

.loading {
    text-align: center;
    color: var(--accent-color);
    margin-top: 15px;
    font-style: italic;
    font-size: 14px;
}

/* Theme Toggle Button */
.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    border: none;
    background: var(--container-bg);
    box-shadow: 0 4px 15px var(--container-shadow);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    transition: all 0.4s ease;
    z-index: 1001;
    padding: 0;
}

.theme-toggle:hover {
    transform: scale(1.1) rotate(15deg);
    box-shadow: 0 6px 20px var(--container-shadow);
}

.theme-toggle:active {
    transform: scale(0.95);
}

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
    position: absolute;
    transition: all 0.4s ease;
}

.theme-toggle .icon-sun {
    opacity: 1;
    transform: rotate(0deg);
}

.theme-toggle .icon-moon {
    opacity: 0;
    transform: rotate(-90deg);
}

[data-theme="dark"] .theme-toggle .icon-sun {
    opacity: 0;
    transform: rotate(90deg);
}

[data-theme="dark"] .theme-toggle .icon-moon {
    opacity: 1;
    transform: rotate(0deg);
}

[data-theme="dark"] .theme-toggle {
    border: 1px solid rgba(127, 90, 240, 0.3);
}

/* Smooth theme transition for all elements */
*, *::before, *::after {
    transition-property: background-color, border-color, color, box-shadow;
    transition-duration: 0.4s;
    transition-timing-function: ease;
}

/* Exclude specific animations from global transition */
button, .theme-toggle, .back-link {
    transition: all 0.3s ease;
}

/* Responsive */
@media (max-width: 768px) {
    body {
        padding: 15px;
    }
    
    .container {
        padding: 25px 20px;
    }
    
    .theme-toggle {
        top: 15px;
        right: 15px;
        width: 44px;
        height: 44px;
        font-size: 20px;
    }
    
    select, input[type="text"], button {
        font-size: 14px;
        padding: 12px;
    }
}