<div class="wrap-collabsible">
    <input id="collapsible3" class="toggle" type="checkbox" />
    <label for="collapsible3" class="lbl-toggle" tabindex="0">Click Me</label>
    <div class="collapsible-content">
        <div class="content-inner">
    <form>
        <input type="text" name="name" placeholder="Name" />
        <input type="email" name="email" placeholder="Email" />
        <textarea name="message" placeholder="Message"></textarea>
        <input type="submit" value="Send" />
        
    </form>
        </div>
    </div>
</div>

input[type="checkbox"] {
    display: none;
}
.wrap-collabsible {
    margin: 1.2rem 0;
}
.lbl-toggle {
    display: block;
    font-weight: bold;
    font-family: monospace;
    font-size: 1.2rem;
    text-transform: uppercase;
    text-align: center;
    padding: 1rem;
    color: #ddd;
    background: #0069ff;
    cursor: pointer;
    border-radius: 7px;
    transition: all 0.25s ease-out;
}
.lbl-toggle:hover {
    color: #fff;
}
.lbl-toggle::before {
    content: " ";
    display: inline-block;
    border-top: 5px solid transparent;
    border-bottom: 5px solid transparent;
    border-left: 5px solid currentColor;
    vertical-align: middle;
    margin-right: 0.7rem;
    transform: translateY(-2px);
    transition: transform 0.2s ease-out;
}
.toggle:checked + .lbl-toggle::before {
    transform: rotate(90deg) translateX(-3px);
}
.collapsible-content {
    max-height: 0px;
    overflow: hidden;
    transition: max-height 0.25s ease-in-out;
}
.toggle:checked + .lbl-toggle + .collapsible-content {
    max-height: 350px;
}
.toggle:checked + .lbl-toggle {
    border-bottom-right-radius: 0;
    border-bottom-left-radius: 0;
}
.collapsible-content .content-inner {
    background: rgba(0, 105, 255, 0.2);
    border-bottom: 1px solid rgba(0, 105, 255, 0.45);
    border-bottom-left-radius: 7px;
    border-bottom-right-radius: 7px;
    padding: 0.5rem 1rem;
}
.collapsible-content form {
   display: flex;
   flex-direction: column;
}
.collapsible-content form > * {
  margin: 1em;
}
.collapsible-content form input[type=submit] {
  display: inline-flex;
  align-self:flex-start;
}