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

html {
    scroll-behavior: smooth;
}

body {
    font-family: Arial, Helvetica, sans-serif;
    background: #f5f7fb;
    color: #1f2937;
    min-height: 100vh;
}

/* Main Container */
.container {
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
    padding: 40px 20px;
}

/* Tool Card */
.tool-card {
    background: #ffffff;
    border: 1px solid #e5e7eb;
    border-radius: 18px;
    padding: 35px;
    box-shadow: 0 10px 35px rgba(0, 0, 0, 0.08);
}

/* Header */
.tool-header {
    text-align: center;
    margin-bottom: 30px;
}

.tool-header h1 {
    font-size: 34px;
    line-height: 1.2;
    margin-bottom: 10px;
    color: #111827;
}

.tool-header p {
    font-size: 16px;
    color: #6b7280;
    line-height: 1.6;
}

/* Password Display */
.password-display {
    display: flex;
    width: 100%;
    gap: 10px;
    margin-bottom: 8px;
}

.password-display input {
    flex: 1;
    min-width: 0;
    height: 56px;
    padding: 0 16px;
    border: 2px solid #d1d5db;
    border-radius: 10px;
    background: #f9fafb;
    color: #111827;
    font-size: 17px;
    font-family: "Courier New", monospace;
    outline: none;
}

.password-display input:focus {
    border-color: #6366f1;
}

.password-display button {
    height: 56px;
    padding: 0 22px;
    border: none;
    border-radius: 10px;
    background: #6366f1;
    color: #ffffff;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: 0.2s ease;
}

.password-display button:hover {
    background: #4f46e5;
}

.password-display button:active {
    transform: scale(0.98);
}

/* Copy Message */
.copy-message {
    min-height: 24px;
    text-align: center;
    color: #16a34a;
    font-size: 14px;
    margin-bottom: 20px;
}

/* Settings */
.settings {
    margin-top: 10px;
}

/* Setting Row */
.setting-row {
    margin-bottom: 25px;
}

.setting-row > label {
    display: block;
    font-size: 16px;
    font-weight: 600;
    color: #111827;
    margin-bottom: 12px;
}

/* Length Control */
.length-control {
    display: flex;
    align-items: center;
    gap: 15px;
}

.length-control input[type="range"] {
    flex: 1;
    width: 100%;
    cursor: pointer;
    accent-color: #6366f1;
}

.length-control span {
    min-width: 48px;
    height: 38px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #eef2ff;
    border: 1px solid #c7d2fe;
    border-radius: 8px;
    color: #4338ca;
    font-size: 15px;
    font-weight: 700;
}

/* Options */
.options {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
    margin-bottom: 25px;
}

.option {
    display: flex;
    align-items: center;
    gap: 10px;
    min-height: 52px;
    padding: 12px 14px;
    border: 1px solid #e5e7eb;
    border-radius: 10px;
    background: #f9fafb;
    cursor: pointer;
    transition: 0.2s ease;
}

.option:hover {
    border-color: #a5b4fc;
    background: #eef2ff;
}

.option input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
    accent-color: #6366f1;
    flex-shrink: 0;
}

.option span {
    font-size: 14px;
    color: #374151;
    line-height: 1.4;
}

/* Generate Button */
.generate-btn {
    width: 100%;
    height: 56px;
    border: none;
    border-radius: 10px;
    background: #111827;
    color: #ffffff;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    transition: 0.2s ease;
    margin-top: 5px;
}

.generate-btn:hover {
    background: #374151;
}

.generate-btn:active {
    transform: scale(0.99);
}

/* Security Information */
.security-info {
    margin-top: 30px;
    padding: 22px;
    border-radius: 12px;
    background: #f9fafb;
    border: 1px solid #e5e7eb;
}

.security-info h2 {
    font-size: 19px;
    color: #111827;
    margin-bottom: 14px;
}

.security-info ul {
    padding-left: 20px;
}

.security-info li {
    color: #6b7280;
    font-size: 14px;
    line-height: 1.7;
    margin-bottom: 5px;
}

.security-info li:last-child {
    margin-bottom: 0;
}

/* Tablet */
@media (max-width: 700px) {

    .container {
        padding: 25px 15px;
    }

    .tool-card {
        padding: 25px 20px;
        border-radius: 14px;
    }

    .tool-header h1 {
        font-size: 28px;
    }

    .options {
        grid-template-columns: 1fr;
    }
}

/* Mobile */
@media (max-width: 480px) {

    .container {
        padding: 15px 10px;
    }

    .tool-card {
        padding: 20px 15px;
    }

    .tool-header {
        margin-bottom: 22px;
    }

    .tool-header h1 {
        font-size: 25px;
    }

    .tool-header p {
        font-size: 14px;
    }

    .password-display {
        flex-direction: column;
    }

    .password-display input {
        width: 100%;
        height: 52px;
        font-size: 15px;
    }

    .password-display button {
        width: 100%;
        height: 50px;
    }

    .length-control {
        gap: 10px;
    }

    .option {
        min-height: 48px;
    }

    .security-info {
        padding: 18px;
    }

    .security-info h2 {
        font-size: 17px;
    }
}

/* Accessibility */
button:focus-visible,
input:focus-visible {
    outline: 3px solid rgba(99, 102, 241, 0.3);
    outline-offset: 2px;
}
```