* { margin: 0; padding: 0; box-sizing: border-box; }
body { 
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif; 
    background: #f0f2f5; 
    padding-bottom: 60px; /* space for bottom nav */
}

/* Top Header - FB Mobile Style */
.header { 
    background: #1877f2; 
    color: white; 
    padding: 12px 16px; 
    position: sticky; 
    top: 0; 
    z-index: 100;
    display: flex; 
    justify-content: space-between; 
    align-items: center;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}
.header h1 { font-size: 22px; font-weight: 700; }
.header a { color: white; text-decoration: none; font-size: 15px; font-weight: 500; }

/* Container */
.container { padding: 10px; max-width: 500px; margin: 0 auto; }

/* Post Box Card */
.post-box { 
    background: white; 
    border-radius: 8px; 
    padding: 12px; 
    margin-bottom: 10px; 
    box-shadow: 0 1px 2px rgba(0,0,0,0.1);
}
.post-box textarea { 
    width: 100%; 
    border: 1px solid #ddd; 
    border-radius: 20px; 
    padding: 8px 12px; 
    font-size: 15px; 
    resize: none; 
    font-family: inherit;
}
.post-box textarea:focus { outline: none; border-color: #1877f2; }
.btn-post { 
    background: #1877f2; 
    color: white; 
    border: none; 
    padding: 8px 24px; 
    border-radius: 6px; 
    font-weight: 600; 
    margin-top: 8px; 
    font-size: 15px;
}

/* Feed Post Card */
.post { 
    background: white; 
    border-radius: 8px; 
    margin-bottom: 10px; 
    box-shadow: 0 1px 2px rgba(0,0,0,0.1);
}
.post-header { 
    display: flex; 
    align-items: center; 
    padding: 12px; 
    gap: 10px;
}
.avatar { 
    width: 40px; 
    height: 40px; 
    border-radius: 50%; 
    background: #1877f2; 
    color: white; 
    display: flex; 
    align-items: center; 
    justify-content: center; 
    font-weight: 600;
}
.post-info strong { font-size: 15px; display: block; }
.post-info span { font-size: 13px; color: #65676b; }
.post-content { padding: 0 12px 12px; font-size: 15px; line-height: 1.4; }
.post-actions { 
    border-top: 1px solid #e4e6eb; 
    display: flex; 
    justify-content: space-around; 
    padding: 4px 0;
}
.post-actions button { 
    flex: 1; 
    background: none; 
    border: none; 
    padding: 8px; 
    color: #65676b; 
    font-weight: 600; 
    font-size: 15px;
}
.post-actions button:active { background: #f0f2f5; }

/* Bottom Nav - Like FB App */
.bottom-nav { 
    position: fixed; 
    bottom: 0; 
    left: 0; 
    right: 0; 
    background: white; 
    border-top: 1px solid #ddd; 
    display: flex; 
    justify-content: space-around; 
    padding: 8px 0;
    z-index: 100;
}
.bottom-nav a { 
    color: #65676b; 
    text-decoration: none; 
    font-size: 12px; 
    text-align: center; 
    flex: 1;
}
.bottom-nav a.active { color: #1877f2; }
.bottom-nav .icon { font-size: 24px; display: block; margin-bottom: 2px; }

/* Auth Pages */
.auth-box { 
    max-width: 400px; 
    margin: 60px auto; 
    background: white; 
    padding: 20px; 
    border-radius: 8px; 
    box-shadow: 0 2px 4px rgba(0,0,0,0.1); 
}
.auth-box h1 { color: #1877f2; text-align: center; margin-bottom: 20px; }
input { 
    width: 100%; 
    padding: 12px; 
    margin: 8px 0; 
    border: 1px solid #ddd; 
    border-radius: 6px; 
    font-size: 16px; 
}
.auth-box button { width: 100%; padding: 12px; font-size: 16px; }
.error { color: #e41e3f; text-align: center; margin: 10px 0; }