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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: #f0f2f5;
    color: #333;
    padding: 32px 16px;
}

header {
    text-align: center;
    margin-bottom: 32px;
}

header h1 {
    font-size: 28px;
    color: #000;
    letter-spacing: 1px;
}

main {
    max-width: 720px;
    margin: 0 auto;
    background: #fff;
    border-radius: 12px;
    padding: 32px;
    box-shadow: 0 2px 16px rgba(0, 0, 0, 0.1);
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

label {
    font-weight: 600;
    font-size: 14px;
    color: #444;
}

select, input[type="text"], textarea {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid #ccc;
    border-radius: 8px;
    font-size: 14px;
    font-family: inherit;
    transition: border-color 0.2s, box-shadow 0.2s;
}

select:focus, input[type="text"]:focus, textarea:focus {
    outline: none;
    border-color: #3498db;
    box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.15);
}

textarea {
    resize: vertical;
    min-height: 120px;
}

textarea[readonly] {
    background: #f9f9f9;
    color: #555;
    cursor: default;
}

.btn-group {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

button {
    padding: 10px 22px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-family: inherit;
    cursor: pointer;
    transition: filter 0.15s, transform 0.1s;
}

button:hover  {
    filter: brightness(0.92);
}

button:active {
    filter: brightness(0.82);
    transform: scale(0.98);
}

#btnEncrypt {
    background: #3498db;
    color: #fff;
}

#btnDecrypt {
    background: #27ae60;
    color: #fff;
}
#btnOpen {
    background: #7f8c8d;
    color: #fff;
}

#btnSave {
    background: #e67e22;
    color: #fff;
}

#toast {
    position: fixed;
    bottom: 32px;
    right: 32px;
    background: #e74c3c;
    color: #fff;
    padding: 12px 20px;
    border-radius: 8px;
    font-size: 14px;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

#toast.show {
    opacity: 1;
    pointer-events: auto;
}