/* main.css - Kiểu dáng cơ bản, font, reset và layout chung */

/* Import font */
@import url('https://fonts.googleapis.com/css2?family=Montserrat:wght@300;400;500;600;700;800&family=Open+Sans:wght@300;400;500;600;700&display=swap');

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

:root {
    /* Primary colors */
    --primary-color: #2563eb;       /* Xanh dương đậm */
    --primary-light: #60a5fa;       /* Xanh dương nhạt */
    --primary-dark: #1e40af;        /* Xanh dương tối */
    
    /* Secondary colors */
    --secondary-color: #10b981;     /* Xanh lá */
    --accent-color: #8b5cf6;        /* Tím */
    
    /* Neutral colors */
    --dark-blue: #0f172a;           /* Xanh đậm gần đen */
    --dark-gray: #1e293b;           /* Xám đậm */
    --medium-gray: #64748b;         /* Xám trung bình */
    --light-gray: #e2e8f0;          /* Xám nhạt */
    --off-white: #f8fafc;           /* Trắng tối */
    
    /* Gradient */
    --gradient-primary: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    
    /* Text colors */
    --text-dark: #0f172a;
    --text-medium: #475569;
    --text-light: #94a3b8;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-xxl: 5rem;
    
    /* Border radius */
    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 16px;
    --border-radius-xl: 24px;
    
    /* Box shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.1);
    
    /* Animation duration */
    --duration-fast: 150ms;
    --duration-normal: 300ms;
    --duration-slow: 500ms;
}

body {
    font-family: 'Open Sans', sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--off-white);
    overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
    font-family: 'Montserrat', sans-serif;
    font-weight: 700;
    line-height: 1.3;
    margin-bottom: var(--spacing-md);
    color: var(--dark-blue);
}

h1 {
    font-size: 3rem;
}

h2 {
    font-size: 2.25rem;
    margin-bottom: var(--spacing-lg);
    text-align: center;
    position: relative;
}

h2::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: var(--gradient-primary);
    border-radius: 2px;
}

h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-sm);
}

p {
    margin-bottom: var(--spacing-md);
}

ul {
    list-style: none;
}

a {
    text-decoration: none;
    color: var(--primary-color);
    transition: color var(--duration-normal);
}

a:hover {
    color: var(--primary-dark);
}

img {
    max-width: 100%;
    height: auto;
    border-radius: var(--border-radius-md);
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

/* Section styling */
section {
    padding: var(--spacing-xxl) 0;
}

section:nth-child(even) {
    background-color: white;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    font-family: 'Montserrat', sans-serif;
    font-weight: 600;
    font-size: 1rem;
    text-align: center;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    border-radius: var(--border-radius-md);
    transition: all var(--duration-normal);
    cursor: pointer;
    border: 2px solid transparent;
}

.btn.primary {
    background-color: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-md);
}

.btn.primary:hover {
    background-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn.secondary {
    background-color: white;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

.btn.large {
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

/* Highlight text */
.highlight {
    font-weight: 600;
    color: var(--primary-dark);
}

.solution {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--secondary-color);
    margin-bottom: var(--spacing-lg);
}

/* Animation utilities */
.fade-in {
    animation: fadeIn var(--duration-slow) ease-in forwards;
}

.slide-in-left {
    animation: slideInLeft var(--duration-slow) ease-out forwards;
}

.slide-in-right {
    animation: slideInRight var(--duration-slow) ease-out forwards;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideInLeft {
    from { transform: translateX(-50px); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

@keyframes slideInRight {
    from { transform: translateX(50px); opacity: 0; }
    to { transform: translateX(0); opacity: 1; }
}

/* Responsive */
@media (max-width: 992px) {
    h1 { font-size: 2.5rem; }
    h2 { font-size: 2rem; }
    section { padding: var(--spacing-xl) 0; }
}

@media (max-width: 768px) {
    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    .container { padding: 0 var(--spacing-md); }
}

@media (max-width: 576px) {
    h1 { font-size: 1.75rem; }
    h2 { font-size: 1.5rem; }
    body { font-size: 15px; }
}

/*Thêm cho thông báo*/
.form-success-message {
    background-color: #4CAF50;
    color: white;
    padding: 15px;
    margin-top: 20px;
    border-radius: 5px;
    text-align: center;
    opacity: 1;
    transition: opacity 0.3s;
}

.form-error-message {
    background-color: #f44336;
    color: white;
    padding: 15px;
    margin-top: 20px;
    border-radius: 5px;
    text-align: center;
    opacity: 1;
    transition: opacity 0.3s;
}