* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background: linear-gradient(135deg, #5a2d0c 0%, #8B4513 30%, #A0522D 70%, #654321 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 500px;
}

.form-container {
    background: rgba(40, 30, 20, 0.85);
    padding: 40px 30px;
    border-radius: 20px;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.5);
    border: 2px solid #8B4513;
    position: relative;
    overflow: hidden;
}
#studentId {
    text-align: left;   /* متن وارد شده */
    direction: ltr;     /* جهت متن از چپ به راست */
}

/* placeholder سمت راست */
#studentId::placeholder {
    text-align: right;  /* فقط placeholder سمت راست */
}
.form-container::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url('logo.jpg') center/cover;
    opacity: 0.08;
    z-index: 0;
}

.form-content {
    position: relative;
    z-index: 1;
}

.header {
    text-align: center;
    margin-bottom: 30px;
}

.header h3 {
    color: #D2B48C;
    font-size: 1.5rem;
    margin-bottom: 10px;
    font-weight: 800;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.5);
}

.header p {
    color: #F5F5DC;
    font-size: 1.1rem;
    opacity: 0.8;
}

.form-group {
    margin-bottom: 25px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    color: #D2B48C;
    font-weight: 600;
    font-size: 1rem;
}

.form-control {
    width: 100%;
    padding: 15px 20px;
    border: 2px solid #654321;
    border-radius: 12px;
    background: rgba(60, 45, 30, 0.9);
    font-size: 1rem;
    color: #F5F5DC;
    transition: all 0.3s ease;
    outline: none;
}

.form-control:focus {
    border-color: #D2B48C;
    background: rgba(70, 55, 40, 0.95);
    box-shadow: 0 0 0 3px rgba(210, 180, 140, 0.2);
    transform: translateY(-2px);
}

.form-control::placeholder {
    color: #A0522D;
    opacity: 0.7;
}

.form-control.invalid {
    border-color: #c0392b;
    box-shadow: 0 0 0 3px rgba(192, 57, 43, 0.2);
}

.error-message {
    color: #e74c3c;
    font-size: 0.85rem;
    margin-top: 5px;
    display: none;
}

.btn-submit {
    width: 100%;
    padding: 16px;
    background: linear-gradient(135deg, #8B4513 0%, #A0522D 100%);
    color: #F5F5DC;
    border: none;
    border-radius: 12px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.4);
    position: relative;
    overflow: hidden;
}

.btn-submit::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
    transition: 0.5s;
}

.btn-submit:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(139, 69, 19, 0.7);
    background: linear-gradient(135deg, #A0522D 0%, #8B4513 100%);
}

.btn-submit:hover::before {
    left: 100%;
}

.btn-submit:active {
    transform: translateY(-1px);
}

.btn-submit:disabled {
    background: #444;
    color: #777;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

/* Responsive Design */
@media (max-width: 768px) {
    .form-container {
        padding: 30px 20px;
        margin: 10px;
    }
    
    .header h3 {
        font-size: 1.3rem;
    }
    
    .form-control {
        padding: 12px 15px;
    }
}

@media (max-width: 480px) {
    body {
        padding: 10px;
    }
    
    .form-container {
        padding: 25px 15px;
    }
    
    .header h3 {
        font-size: 1.2rem;
    }
    
    .header p {
        font-size: 1rem;
    }
    
    .btn-submit {
        padding: 14px;
        font-size: 1rem;
    }
}

/* Animation */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.form-container {
    animation: fadeInUp 0.6s ease-out;
}

.form-group {
    animation: fadeInUp 0.6s ease-out;
    animation-fill-mode: both;
}

.form-group:nth-child(1) { animation-delay: 0.1s; }
.form-group:nth-child(2) { animation-delay: 0.2s; }
.form-group:nth-child(3) { animation-delay: 0.3s; }
.form-group:nth-child(4) { animation-delay: 0.4s; }
.btn-submit { animation-delay: 0.5s; }