Interactive OTP Sign In form | HTML, CSS & JavaScript

<div class="card">
        <div class="badge"><span class="badge-dot"></span> SECURE AUTH</div>

<div id="step1" class="step active">
            <h2>Sign in</h2>
            <p class="sub">Access your account via secure code.</p>

<div class="method-toggle">
                <button class="method-btn active" onclick="setMethod('phone')">Phone</button>
                <button class="method-btn" onclick="setMethod('email')">Email</button>
            </div>

<div id="phoneField">
                <label>Phone Number</label>
                <div class="input-row">
                    <div
                        style="background: var(--bg-input); border: 1px solid var(--border); padding: 0 12px; border-radius: 10px; display: flex; align-items: center; font-size: 14px; color: var(--text-sub);">
                        🇺🇸 +1</div>
                    <input type="tel" id="phoneInput" placeholder="(555) 000-0000">
                </div>
            </div>

<div id="emailField" style="display: none;">
                <label>Email Address</label>
                <input type="email" id="emailInput" placeholder="hello@design.com" style="margin-bottom: 1.5rem;">
            </div>

<div id="step2" class="step">
            <h2>Enter Code</h2>
            <p class="sub">Sent to <strong id="displayTarget" style="color:#fff;"></strong></p>

<div class="otp-container">
                <input type="text" maxlength="1" class="otp-input" oninput="moveNext(this, 0)">
                <input type="text" maxlength="1" class="otp-input" oninput="moveNext(this, 1)">
                <input type="text" maxlength="1" class="otp-input" oninput="moveNext(this, 2)">
                <input type="text" maxlength="1" class="otp-input" oninput="moveNext(this, 3)">
                <input type="text" maxlength="1" class="otp-input" oninput="moveNext(this, 4)">
                <input type="text" maxlength="1" class="otp-input" oninput="moveNext(this, 5)">
            </div>
            <div id="errorCode" class="error">Invalid code. Demo: 246810</div>

<button class="btn" onclick="verifyCode()">Verify Identity</button>
            <a class="back-link" onclick="goBack()">← Back to options</a>
        </div>

<div id="step3" class="step" style="text-align: center; padding: 1rem 0;">
            <div style="font-size: 60px; margin-bottom: 1.5rem;">✨</div>
            <h2 style="color: #1D9E75;">Success!</h2>
            <p class="sub">You've successfully authenticated.</p>
            <button class="btn" onclick="location.reload()">Return to Home</button>
        </div>
    </div>

@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;700&family=Space+Mono:wght@400;700&display=swap');

:root {
    --primary: #7F77DD;
    --primary-glow: rgba(127, 119, 221, 0.3);
    --bg-body: #0f1115;
    --bg-card: #1c1f26;
    --bg-input: #12141a;
    --text-main: #ffffff;
    --text-sub: #9ca3af;
    --border: #2d3139;
    --radius: 16px;
}

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

body {
    background: var(--bg-body);
    font-family: 'DM Sans', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    color: var(--text-main);
}

.card {
    background: var(--bg-card);
    width: 100%;
    max-width: 400px;
    padding: 2.5rem;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    box-shadow: 0 20px 50px rgba(0, 0, 0, 0.5);
    position: relative;
    overflow: hidden;
}

/* Animated Accent Bar */
.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, #7F77DD, #1D9E75, #7F77DD);
    background-size: 200% 100%;
    animation: shimmer 4s linear infinite;
}

@keyframes shimmer {
    0% {
        background-position: 0% 0%;
    }

100% {
        background-position: 200% 0%;
    }
}

.badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: rgba(255, 255, 255, 0.05);
    padding: 6px 12px;
    border-radius: 99px;
    font-size: 11px;
    font-family: 'Space Mono', monospace;
    color: var(--text-sub);
    margin-bottom: 1.5rem;
    border: 1px solid var(--border);
}

.badge-dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: #1D9E75;
    box-shadow: 0 0 8px #1D9E75;
}

.step {
    display: none;
}

.step.active {
    display: block;
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

to {
        opacity: 1;
        transform: translateY(0);
    }
}

.method-toggle {
    display: flex;
    background: var(--bg-input);
    padding: 4px;
    border-radius: 10px;
    margin-bottom: 2rem;
    border: 1px solid var(--border);
}

.method-btn {
    flex: 1;
    padding: 10px;
    border: none;
    background: transparent;
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    border-radius: 8px;
    color: var(--text-sub);
    transition: 0.3s;
}

.method-btn.active {
    background: var(--border);
    color: #fff;
}

h2 {
    font-size: 24px;
    margin-bottom: 8px;
}

p.sub {
    font-size: 14px;
    color: var(--text-sub);
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

label {
    display: block;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 8px;
    color: var(--text-sub);
}

.input-row {
    display: flex;
    gap: 10px;
    margin-bottom: 1.5rem;
}

input {
    width: 100%;
    height: 48px;
    padding: 0 16px;
    background: var(--bg-input);
    border: 1px solid var(--border);
    border-radius: 10px;
    font-size: 15px;
    color: #fff;
    outline: none;
    transition: 0.2s;
}

input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 4px var(--primary-glow);
}

.btn {
    width: 100%;
    height: 48px;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 10px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    box-shadow: 0 4px 15px rgba(127, 119, 221, 0.4);
}

.btn:hover {
    transform: translateY(-1px);
    opacity: 0.95;
}

.btn:active {
    transform: translateY(0);
}

.otp-container {
    display: flex;
    gap: 8px;
    justify-content: space-between;
    margin-bottom: 2rem;
}

.otp-input {
    width: 48px;
    height: 60px;
    text-align: center;
    font-size: 22px;
    font-family: 'Space Mono', monospace;
    font-weight: 700;
    background: var(--bg-input);
}

.error {
    color: #ff5f5f;
    font-size: 13px;
    text-align: center;
    margin-bottom: 1rem;
    display: none;
}

.back-link {
    display: block;
    text-align: center;
    margin-top: 1.5rem;
    font-size: 13px;
    color: var(--text-sub);
    cursor: pointer;
    transition: 0.2s;
}

.back-link:hover {
    color: #fff;
}

let currentMethod = 'phone';
        const DEMO_CODE = "246810";

function setMethod(method) {
            currentMethod = method;
            document.querySelectorAll('.method-btn').forEach(btn => btn.classList.remove('active'));
            event.target.classList.add('active');

document.getElementById('phoneField').style.display = method === 'phone' ? 'block' : 'none';
            document.getElementById('emailField').style.display = method === 'email' ? 'block' : 'none';
        }

function sendCode() {
            const target = currentMethod === 'phone' ?
                document.getElementById('phoneInput').value :
                document.getElementById('emailInput').value;

if (!target) return;

document.getElementById('displayTarget').innerText = target;
            document.getElementById('step1').classList.remove('active');
            document.getElementById('step2').classList.add('active');
            document.querySelectorAll('.otp-input')[0].focus();
        }

function moveNext(el, index) {
            const inputs = document.querySelectorAll('.otp-input');
            if (el.value && index < 5) {
                inputs[index + 1].focus();
            }
        }

function verifyCode() {
            const inputs = document.querySelectorAll('.otp-input');
            let code = "";
            inputs.forEach(input => code += input.value);

if (code === DEMO_CODE) {
                document.getElementById('step2').classList.remove('active');
                document.getElementById('step3').classList.add('active');
            } else {
                document.getElementById('errorCode').style.display = 'block';
                inputs.forEach(input => {
                    input.value = "";
                    input.style.borderColor = "#ff5f5f";
                });
                inputs[0].focus();
            }
        }

function goBack() {
            document.getElementById('step2').classList.remove('active');
            document.getElementById('step1').classList.add('active');
            document.getElementById('errorCode').style.display = 'none';
        }

- Interactive OTP Sign In form

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