/* =========================================================
   看中文填单词 - 自适应移动端虚拟字母键盘样式表
   (web/zh2en_input/keyboard.css)
   ========================================================= */

.virtual-keyboard {
    width: 100%;
    max-width: 480px;
    margin: auto auto 0;
    padding: clamp(4px, 0.8vh, 8px) 4px clamp(6px, 1vh, 10px);
    background: #f1f5f9;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.04);
    touch-action: manipulation;
    -webkit-tap-highlight-color: transparent;
    user-select: none;
    -webkit-user-select: none;
    box-sizing: border-box;
}

.keyboard-row {
    display: flex;
    width: 100%;
    gap: clamp(3px, 1vw, 5px);
    margin-bottom: clamp(4px, 0.8vh, 6px);
    align-items: stretch;
    box-sizing: border-box;
}

.keyboard-row:last-child {
    margin-bottom: 0;
}

/* 基础按键设计 */
.key-btn {
    flex: 1;
    height: clamp(38px, 5.5vh, 46px);
    border: 1.5px solid #cbd5e1;
    border-bottom: 3px solid #94a3b8;
    background: #ffffff;
    color: #1e293b;
    border-radius: 8px;
    font-size: clamp(1.05rem, 3vw, 1.22rem);
    font-weight: 700;
    font-family: inherit;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    outline: none;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
    transition: all 0.08s ease-out;
    padding: 0;
    box-sizing: border-box;
}

.key-btn:active {
    transform: translateY(2px);
    border-bottom-width: 1.5px;
    background: #e2e8f0;
}

/* 占位间隙按键 (Row 2 居中对齐) */
.key-spacer {
    flex: 0.5;
    pointer-events: none;
    visibility: hidden;
}

/* 退格键 */
.key-backspace {
    flex: 2;
    background: #f8fafc;
    border-color: #cbd5e1;
    border-bottom-color: #94a3b8;
    color: #475569;
    font-size: 1.25rem;
}

.key-backspace:active {
    background: #e2e8f0;
}

/* 清空键 */
.key-clear {
    flex: 1.5;
    background: #fff1f2;
    border-color: #fecdd3;
    border-bottom-color: #f43f5e;
    color: #e11d48;
    font-size: 0.85rem;
}

.key-clear:active {
    background: #ffe4e6;
}

/* 连字符与撇号按键 */
.key-symbol {
    flex: 1;
    background: #f8fafc;
    color: #334155;
    font-size: 1.15rem;
}

/* 空格键 */
.key-space {
    flex: 4.5;
    background: #ffffff;
    border-color: #cbd5e1;
    border-bottom-color: #94a3b8;
    color: #64748b;
    font-size: 0.85rem;
    letter-spacing: 1px;
}

/* 键盘内置快捷提交按键 */
.key-submit {
    flex: 3;
    background: linear-gradient(135deg, #4f46e5, #4338ca);
    border-color: #4338ca;
    border-bottom-color: #312e81;
    color: #ffffff;
    font-size: 0.92rem;
    box-shadow: 0 2px 6px rgba(79, 70, 229, 0.35);
}

.key-submit:active {
    background: #3730a3;
}

/* 键盘禁用态 */
.virtual-keyboard.disabled {
    opacity: 0.55;
    pointer-events: none;
}

/* 移动端细屏适配 (< 370px) */
@media (max-width: 370px) {
    .virtual-keyboard {
        padding: 4px 2px 6px;
    }
    .keyboard-row {
        gap: 3px;
        margin-bottom: 4px;
    }
    .key-btn {
        height: 40px;
        font-size: 1.05rem;
        border-radius: 6px;
    }
    .key-clear, .key-space, .key-submit {
        font-size: 0.78rem;
    }
}

/* =========================================================
   互动下划线字母卡槽 (Letter Slots)
   ========================================================= */
.slots-container {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: clamp(6px, 1.5vw, 10px) clamp(8px, 2.5vw, 14px);
    margin: clamp(6px, 1.2vh, 14px) auto clamp(4px, 0.8vh, 8px);
    padding: clamp(6px, 1vh, 10px) 4px;
    min-height: clamp(52px, 8vh, 64px);
    box-sizing: border-box;
    user-select: none;
    -webkit-user-select: none;
}

.word-slot-group {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    flex-shrink: 0;
}

.slot-item {
    width: clamp(34px, 8.5vw, 42px);
    height: clamp(44px, 6vh, 50px);
    border: 2px solid #cbd5e1;
    border-bottom: 4px solid #64748b;
    border-radius: 8px;
    background: #ffffff;
    color: #1e293b;
    font-size: clamp(1.3rem, 4vw, 1.55rem);
    font-weight: 800;
    font-family: 'Segoe UI', -apple-system, system-ui, sans-serif;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
    position: relative;
    cursor: pointer;
    transition: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    box-sizing: border-box;
}

/* 当前激活输入光标 */
.slot-item.active {
    border-color: #4f46e5;
    border-bottom-color: #4338ca;
    background: #eef2ff;
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.2);
    transform: translateY(-2px);
}

.slot-item.active::after {
    content: '';
    position: absolute;
    bottom: 5px;
    width: 14px;
    height: 3px;
    background: #4f46e5;
    border-radius: 2px;
    animation: slotBlink 0.9s infinite;
}

@keyframes slotBlink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0; }
}

/* 已填入字母 */
.slot-item.filled {
    border-color: #94a3b8;
    border-bottom-color: #475569;
    animation: slotPop 0.15s ease-out;
}

@keyframes slotPop {
    0% { transform: scale(0.88); }
    60% { transform: scale(1.06); }
    100% { transform: scale(1); }
}

/* 提示给出的字母 */
.slot-item.hinted {
    background: #fffbeb !important;
    border-color: #f59e0b !important;
    border-bottom-color: #d97706 !important;
    color: #b45309 !important;
}

/* 固定标点 (如 ' 或 -) */
.slot-item.slot-fixed {
    width: 18px;
    border: none;
    border-bottom: none;
    background: transparent;
    box-shadow: none;
    color: #475569;
    font-size: 1.5rem;
    cursor: default;
}

/* 正确绿色反馈 */
.slot-item.correct {
    border-color: #22c55e !important;
    border-bottom-color: #16a34a !important;
    background: #f0fdf4 !important;
    color: #15803d !important;
    transform: scale(1.03);
}

/* 错误红色反馈 */
.slot-item.wrong {
    border-color: #ef4444 !important;
    border-bottom-color: #dc2626 !important;
    background: #fef2f2 !important;
    color: #b91c1c !important;
}

/* 窄屏设备自适应 */
@media (max-width: 380px) {
    .slot-item {
        width: 31px;
        height: 42px;
        font-size: 1.2rem;
    }
    .word-slot-group {
        gap: 4px;
    }
}