/* Design System for All About Material (PHP Version) */
:root {
    --primary: #1A1A1A;
    --primary-light: #333333;
    --accent: #E63946;
    --accent-hover: #C52D3A;
    --bg-main: #F8F9FA;
    --surface: #FFFFFF;
    --text-main: #1A202C;
    --text-muted: #718096;
    --border: #E2E8F0;
    --radius: 8px;
    --font-main: 'Inter', system-ui, sans-serif;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: var(--font-main);
    background-color: var(--bg-main);
    color: var(--text-main);
    line-height: 1.6;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.section { padding: 80px 0; }

header {
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 16px 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-flex { display: flex; justify-content: space-between; align-items: center; }
.nav-links { display: flex; gap: 24px; align-items: center; }
.nav-link { font-weight: 500; font-size: 0.95rem; text-decoration: none; color: inherit; }
.nav-link:hover { color: var(--accent); }

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    border-radius: var(--radius);
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    border: none;
    transition: all 0.2s;
}

.btn-primary { background: var(--primary); color: white; }
.btn-accent { background: var(--accent); color: white; }
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text-main); }
.btn-outline:hover { background: #f1f5f9; }

.card { background: white; border-radius: var(--radius); border: 1px solid var(--border); padding: 24px; box-shadow: var(--shadow-sm); }
.grid-3 { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 32px; }

.form-group { margin-bottom: 20px; }
.label { display: block; margin-bottom: 8px; font-weight: 500; font-size: 0.9rem; }
.input { width: 100%; padding: 12px; border: 1px solid var(--border); border-radius: var(--radius); outline: none; }
.input:focus { border-color: var(--primary); }

.alert { padding: 16px; border-radius: var(--radius); margin-bottom: 24px; }
.alert-success { background: #C6F6D5; color: #22543D; border: 1px solid #9AE6B4; }
.alert-danger { background: #FED7D7; color: #822727; border: 1px solid #FEB2B2; }

.text-muted { color: var(--text-muted); }
.text-center { text-align: center; }
.mb-4 { margin-bottom: 16px; }
.mb-8 { margin-bottom: 32px; }
.mt-4 { margin-top: 16px; }
.flex { display: flex; align-items: center; gap: 8px; }
.badge { padding: 4px 12px; border-radius: 99px; font-size: 0.75rem; font-weight: 600; }